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[PATCH v13 6/8] Row pattern recognition patch (docs). 319+ messages / 2 participants [nested] [flat]
* [PATCH v13 6/8] Row pattern recognition patch (docs). @ 2024-01-22 09:45 Tatsuo Ishii <ishii@postgresql.org> 0 siblings, 0 replies; 319+ messages in thread From: Tatsuo Ishii @ 2024-01-22 09:45 UTC (permalink / raw) --- doc/src/sgml/advanced.sgml | 80 ++++++++++++++++++++++++++++++++++++ doc/src/sgml/func.sgml | 54 ++++++++++++++++++++++++ doc/src/sgml/ref/select.sgml | 38 ++++++++++++++++- 3 files changed, 170 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/advanced.sgml b/doc/src/sgml/advanced.sgml index 755c9f1485..cf18dd887e 100644 --- a/doc/src/sgml/advanced.sgml +++ b/doc/src/sgml/advanced.sgml @@ -537,6 +537,86 @@ WHERE pos < 3; <literal>rank</literal> less than 3. </para> + <para> + Row pattern common syntax can be used to perform row pattern recognition + in a query. Row pattern common syntax includes two sub + clauses: <literal>DEFINE</literal> + and <literal>PATTERN</literal>. <literal>DEFINE</literal> defines + definition variables along with an expression. The expression must be a + logical expression, which means it must + return <literal>TRUE</literal>, <literal>FALSE</literal> + or <literal>NULL</literal>. The expression may comprise column references + and functions. Window functions, aggregate functions and subqueries are + not allowed. An example of <literal>DEFINE</literal> is as follows. + +<programlisting> +DEFINE + LOWPRICE AS price <= 100, + UP AS price > PREV(price), + DOWN AS price < PREV(price) +</programlisting> + + Note that <function>PREV</function> returns the price column in the + previous row if it's called in a context of row pattern recognition. So in + the second line the definition variable "UP" is <literal>TRUE</literal> + when the price column in the current row is greater than the price column + in the previous row. Likewise, "DOWN" is <literal>TRUE</literal> when when + the price column in the current row is lower than the price column in the + previous row. + </para> + <para> + Once <literal>DEFINE</literal> exists, <literal>PATTERN</literal> can be + used. <literal>PATTERN</literal> defines a sequence of rows that satisfies + certain conditions. For example following <literal>PATTERN</literal> + defines that a row starts with the condition "LOWPRICE", then one or more + rows satisfy "UP" and finally one or more rows satisfy "DOWN". Note that + "+" means one or more matches. Also you can use "*", which means zero or + more matches. If a sequence of rows which satisfies the PATTERN is found, + in the starting row of the sequence of rows all window functions and + aggregates are shown in the target list. Note that aggregations only look + into the matched rows, rather than whole frame. In the second or + subsequent rows all window functions and aggregates are NULL. For rows + that do not match the PATTERN, all window functions and aggregates are + shown AS NULL too, except count which shows 0. This is because the + unmatched rows are in an empty frame. Example of + a <literal>SELECT</literal> using the <literal>DEFINE</literal> + and <literal>PATTERN</literal> clause is as follows. + +<programlisting> +SELECT company, tdate, price, + first_value(price) OVER w, + max(price) OVER w, + count(price) OVER w +FROM stock, + WINDOW w AS ( + PARTITION BY company + ORDER BY tdate + ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING + AFTER MATCH SKIP PAST LAST ROW + INITIAL + PATTERN (LOWPRICE UP+ DOWN+) + DEFINE + LOWPRICE AS price <= 100, + UP AS price > PREV(price), + DOWN AS price < PREV(price) +); +</programlisting> +<screen> + company | tdate | price | first_value | max | count +----------+------------+-------+-------------+-----+------- + company1 | 2023-07-01 | 100 | 100 | 200 | 4 + company1 | 2023-07-02 | 200 | | | + company1 | 2023-07-03 | 150 | | | + company1 | 2023-07-04 | 140 | | | + company1 | 2023-07-05 | 150 | | | 0 + company1 | 2023-07-06 | 90 | 90 | 130 | 4 + company1 | 2023-07-07 | 110 | | | + company1 | 2023-07-08 | 130 | | | + company1 | 2023-07-09 | 120 | | | + company1 | 2023-07-10 | 130 | | | 0 +</screen> + </para> + <para> When a query involves multiple window functions, it is possible to write out each one with a separate <literal>OVER</literal> clause, but this is diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 210c7c0b02..8422aa6b93 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -21941,6 +21941,7 @@ SELECT count(*) FROM sometable; returns <literal>NULL</literal> if there is no such row. </para></entry> </row> + </tbody> </tgroup> </table> @@ -21980,6 +21981,59 @@ SELECT count(*) FROM sometable; Other frame specifications can be used to obtain other effects. </para> + <para> + Row pattern recognition navigation functions are listed in + <xref linkend="functions-rpr-navigation-table"/>. These functions + can be used to describe DEFINE clause of Row pattern recognition. + </para> + + <table id="functions-rpr-navigation-table"> + <title>Row Pattern Navigation Functions</title> + <tgroup cols="1"> + <thead> + <row> + <entry role="func_table_entry"><para role="func_signature"> + Function + </para> + <para> + Description + </para></entry> + </row> + </thead> + + <tbody> + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>prev</primary> + </indexterm> + <function>prev</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <returnvalue>anyelement</returnvalue> + </para> + <para> + Returns the column value at the previous row; + returns NULL if there is no previous row in the window frame. + </para></entry> + </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>next</primary> + </indexterm> + <function>next</function> ( <parameter>value</parameter> <type>anyelement</type> ) + <returnvalue>anyelement</returnvalue> + </para> + <para> + Returns the column value at the next row; + returns NULL if there is no next row in the window frame. + </para></entry> + </row> + + </tbody> + </tgroup> + </table> + <note> <para> The SQL standard defines a <literal>RESPECT NULLS</literal> or diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml index 9917df7839..1575fc2167 100644 --- a/doc/src/sgml/ref/select.sgml +++ b/doc/src/sgml/ref/select.sgml @@ -969,8 +969,8 @@ WINDOW <replaceable class="parameter">window_name</replaceable> AS ( <replaceabl The <replaceable class="parameter">frame_clause</replaceable> can be one of <synopsis> -{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ] -{ RANGE | ROWS | GROUPS } BETWEEN <replaceable>frame_start</replaceable> AND <replaceable>frame_end</replaceable> [ <replaceable>frame_exclusion</replaceable> ] +{ RANGE | ROWS | GROUPS } <replaceable>frame_start</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [row_pattern_common_syntax] +{ RANGE | ROWS | GROUPS } BETWEEN <replaceable>frame_start</replaceable> AND <replaceable>frame_end</replaceable> [ <replaceable>frame_exclusion</replaceable> ] [row_pattern_common_syntax] </synopsis> where <replaceable>frame_start</replaceable> @@ -1077,6 +1077,40 @@ EXCLUDE NO OTHERS a given peer group will be in the frame or excluded from it. </para> + <para> + The + optional <replaceable class="parameter">row_pattern_common_syntax</replaceable> + defines the <firstterm>row pattern recognition condition</firstterm> for + this + window. <replaceable class="parameter">row_pattern_common_syntax</replaceable> + includes following subclauses. <literal>AFTER MATCH SKIP PAST LAST + ROW</literal> or <literal>AFTER MATCH SKIP TO NEXT ROW</literal> controls + how to proceed to next row position after a match + found. With <literal>AFTER MATCH SKIP PAST LAST ROW</literal> (the + default) next row position is next to the last row of previous match. On + the other hand, with <literal>AFTER MATCH SKIP TO NEXT ROW</literal> next + row position is always next to the last row of previous + match. <literal>DEFINE</literal> defines definition variables along with a + boolean expression. <literal>PATTERN</literal> defines a sequence of rows + that satisfies certain conditions using variables defined + in <literal>DEFINE</literal> clause. If the variable is not defined in + the <literal>DEFINE</literal> clause, it is implicitly assumed + following is defined in the <literal>DEFINE</literal> clause. + +<synopsis> +<literal>variable_name</literal> AS TRUE +</synopsis> + + Note that the maximu number of variables defined + in <literal>DEFINE</literal> clause is 26. + +<synopsis> +[ AFTER MATCH SKIP PAST LAST ROW | AFTER MATCH SKIP TO NEXT ROW ] +PATTERN <replaceable class="parameter">pattern_variable_name</replaceable>[+] [, ...] +DEFINE <replaceable class="parameter">definition_varible_name</replaceable> AS <replaceable class="parameter">expression</replaceable> [, ...] +</synopsis> + </para> + <para> The purpose of a <literal>WINDOW</literal> clause is to specify the behavior of <firstterm>window functions</firstterm> appearing in the query's -- 2.25.1 ----Next_Part(Mon_Jan_22_19_26_18_2024_011)-- Content-Type: Text/X-Patch; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="v13-0007-Row-pattern-recognition-patch-tests.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers @ 2025-02-24 19:08 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-02-24 19:08 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 19 ++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 5 +- src/backend/storage/buffer/freelist.c | 4 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 99 insertions(+), 36 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 62f01d8218a..59aa67cb135 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -149,8 +149,13 @@ static int next_free_segment = 0; * 7f4718400000-7f4718401000 /usr/lib64/libicudata.so.74.2 * ... */ -Size SHMEM_EXTRA_SIZE_LIMIT[1] = { - 0, /* MAIN_SHMEM_SLOT */ +Size SHMEM_EXTRA_SIZE_LIMIT[6] = { + 0, /* MAIN_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 10, /* BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 1024 * 1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* BUFFER_IOCV_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + (Size) 1024 * 1024 * 100, /* STRATEGY_SHMEM_SEGMENT */ }; /* Remembers offset of the last mapping from the probe address */ @@ -179,6 +184,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1f8e03190..f5b9290a640 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -61,7 +61,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -73,22 +76,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -98,8 +101,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -153,33 +157,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..ac449954dab 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -59,10 +59,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..4919a92f2be 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -491,9 +491,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 4f6c707c204..68778522591 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -112,7 +112,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 7c1e4316dde..bb7fe02e243 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -297,7 +297,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 138078c29c5..ba0192baf95 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -105,7 +105,29 @@ extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --q7xzg7duksj2kgko Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v2-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers @ 2025-03-15 15:38 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-03-15 15:38 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index a0f03ff868f..f46d9d5d9cd 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -147,10 +147,18 @@ static int next_free_segment = 0; * * The reserved space pointer is calculated to slice up the total reserved * space into fixed fractions of address space for each segment, as specified - * in the SHMEM_RESIZE_RATIO array. + * in the SHMEM_RESIZE_RATIO array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take + * up to 60% of the whole space when resizing, based on the fact that it most + * likely will be the main consumer of this memory. Those numbers are pulled + * out of thin air for now, makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -182,6 +190,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 336715b6c63..81543cb5ced 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 076888c0172..9d00b80b4f8 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index f2192ceb271..1977001e533 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -308,7 +308,7 @@ extern bool EvictUnpinnedBuffer(Buffer buf); /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 4a83e255652..c5009a1cd73 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -107,7 +107,29 @@ extern void PGSharedMemoryDetach(void); extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags); void *ReserveAnonymousMemory(Size reserve_size); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.45.1 --vninua6xybvzgrci Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v4-0004-Introduce-pending-flag-for-GUC-assign-hooks.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
* [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers @ 2025-06-17 09:22 Dmitrii Dolgov <9erthalion6@gmail.com> 0 siblings, 0 replies; 319+ messages in thread From: Dmitrii Dolgov @ 2025-06-17 09:22 UTC (permalink / raw) Add more shmem segments to split shared buffers into following chunks: * BUFFERS_SHMEM_SEGMENT: contains buffer blocks * BUFFER_DESCRIPTORS_SHMEM_SEGMENT: contains buffer descriptors * BUFFER_IOCV_SHMEM_SEGMENT: contains condition variables for buffers * CHECKPOINT_BUFFERS_SHMEM_SEGMENT: contains checkpoint buffer ids * STRATEGY_SHMEM_SEGMENT: contains buffer strategy status Size of the corresponding shared data directly depends on NBuffers, meaning that if we would like to change NBuffers, they have to be resized correspondingly. Placing each of them in a separate shmem segment allows to achieve that. There are some asumptions made about each of shmem segments upper size limit. The buffer blocks have the largest, while the rest claim less extra room for resize. Ideally those limits have to be deduced from the maximum allowed shared memory. --- src/backend/port/sysv_shmem.c | 24 +++++++- src/backend/storage/buffer/buf_init.c | 79 +++++++++++++++++--------- src/backend/storage/buffer/buf_table.c | 6 +- src/backend/storage/buffer/freelist.c | 5 +- src/backend/storage/ipc/ipci.c | 2 +- src/include/storage/bufmgr.h | 2 +- src/include/storage/pg_shmem.h | 24 +++++++- 7 files changed, 105 insertions(+), 37 deletions(-) diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index 363ddfd1fca..dac011b766b 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -139,10 +139,18 @@ static int next_free_segment = 0; * * The reserved space for each segment is calculated as a fraction of the total * reserved space (MaxAvailableMemory), as specified in the SHMEM_RESIZE_RATIO - * array. + * array. E.g. we allow BUFFERS_SHMEM_SEGMENT to take up to 60% of the whole + * space when resizing, based on the fact that it most likely will be the main + * consumer of this memory. Those numbers are pulled out of thin air for now, + * makes sense to evaluate them more precise. */ -static double SHMEM_RESIZE_RATIO[1] = { - 1.0, /* MAIN_SHMEM_SLOT */ +static double SHMEM_RESIZE_RATIO[6] = { + 0.1, /* MAIN_SHMEM_SEGMENT */ + 0.6, /* BUFFERS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_DESCRIPTORS_SHMEM_SEGMENT */ + 0.1, /* BUFFER_IOCV_SHMEM_SEGMENT */ + 0.05, /* CHECKPOINT_BUFFERS_SHMEM_SEGMENT */ + 0.05, /* STRATEGY_SHMEM_SEGMENT */ }; /* @@ -167,6 +175,16 @@ MappingName(int shmem_segment) { case MAIN_SHMEM_SEGMENT: return "main"; + case BUFFERS_SHMEM_SEGMENT: + return "buffers"; + case BUFFER_DESCRIPTORS_SHMEM_SEGMENT: + return "descriptors"; + case BUFFER_IOCV_SHMEM_SEGMENT: + return "iocv"; + case CHECKPOINT_BUFFERS_SHMEM_SEGMENT: + return "checkpoint"; + case STRATEGY_SHMEM_SEGMENT: + return "strategy"; default: return "unknown"; } diff --git a/src/backend/storage/buffer/buf_init.c b/src/backend/storage/buffer/buf_init.c index ed1dc488a42..bd68b69ee98 100644 --- a/src/backend/storage/buffer/buf_init.c +++ b/src/backend/storage/buffer/buf_init.c @@ -62,7 +62,10 @@ CkptSortItem *CkptBufferIds; * Initialize shared buffer pool * * This is called once during shared-memory initialization (either in the - * postmaster, or in a standalone backend). + * postmaster, or in a standalone backend). Size of data structures initialized + * here depends on NBuffers, and to be able to change NBuffers without a + * restart we store each structure into a separate shared memory segment, which + * could be resized on demand. */ void BufferManagerShmemInit(void) @@ -74,22 +77,22 @@ BufferManagerShmemInit(void) /* Align descriptors to a cacheline boundary. */ BufferDescriptors = (BufferDescPadded *) - ShmemInitStruct("Buffer Descriptors", + ShmemInitStructInSegment("Buffer Descriptors", NBuffers * sizeof(BufferDescPadded), - &foundDescs); + &foundDescs, BUFFER_DESCRIPTORS_SHMEM_SEGMENT); /* Align buffer pool on IO page size boundary. */ BufferBlocks = (char *) TYPEALIGN(PG_IO_ALIGN_SIZE, - ShmemInitStruct("Buffer Blocks", + ShmemInitStructInSegment("Buffer Blocks", NBuffers * (Size) BLCKSZ + PG_IO_ALIGN_SIZE, - &foundBufs)); + &foundBufs, BUFFERS_SHMEM_SEGMENT)); /* Align condition variables to cacheline boundary. */ BufferIOCVArray = (ConditionVariableMinimallyPadded *) - ShmemInitStruct("Buffer IO Condition Variables", + ShmemInitStructInSegment("Buffer IO Condition Variables", NBuffers * sizeof(ConditionVariableMinimallyPadded), - &foundIOCV); + &foundIOCV, BUFFER_IOCV_SHMEM_SEGMENT); /* * The array used to sort to-be-checkpointed buffer ids is located in @@ -99,8 +102,9 @@ BufferManagerShmemInit(void) * painful. */ CkptBufferIds = (CkptSortItem *) - ShmemInitStruct("Checkpoint BufferIds", - NBuffers * sizeof(CkptSortItem), &foundBufCkpt); + ShmemInitStructInSegment("Checkpoint BufferIds", + NBuffers * sizeof(CkptSortItem), &foundBufCkpt, + CHECKPOINT_BUFFERS_SHMEM_SEGMENT); if (foundDescs || foundBufs || foundIOCV || foundBufCkpt) { @@ -156,33 +160,54 @@ BufferManagerShmemInit(void) * BufferManagerShmemSize * * compute the size of shared memory for the buffer pool including - * data pages, buffer descriptors, hash tables, etc. + * data pages, buffer descriptors, hash tables, etc. based on the + * shared memory segment. The main segment must not allocate anything + * related to buffers, every other segment will receive part of the + * data. */ Size -BufferManagerShmemSize(void) +BufferManagerShmemSize(int shmem_segment) { Size size = 0; - /* size of buffer descriptors */ - size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); - /* to allow aligning buffer descriptors */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == MAIN_SHMEM_SEGMENT) + return size; - /* size of data pages, plus alignment padding */ - size = add_size(size, PG_IO_ALIGN_SIZE); - size = add_size(size, mul_size(NBuffers, BLCKSZ)); + if (shmem_segment == BUFFER_DESCRIPTORS_SHMEM_SEGMENT) + { + /* size of buffer descriptors */ + size = add_size(size, mul_size(NBuffers, sizeof(BufferDescPadded))); + /* to allow aligning buffer descriptors */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } - /* size of stuff controlled by freelist.c */ - size = add_size(size, StrategyShmemSize()); + if (shmem_segment == BUFFERS_SHMEM_SEGMENT) + { + /* size of data pages, plus alignment padding */ + size = add_size(size, PG_IO_ALIGN_SIZE); + size = add_size(size, mul_size(NBuffers, BLCKSZ)); + } - /* size of I/O condition variables */ - size = add_size(size, mul_size(NBuffers, - sizeof(ConditionVariableMinimallyPadded))); - /* to allow aligning the above */ - size = add_size(size, PG_CACHE_LINE_SIZE); + if (shmem_segment == STRATEGY_SHMEM_SEGMENT) + { + /* size of stuff controlled by freelist.c */ + size = add_size(size, StrategyShmemSize()); + } - /* size of checkpoint sort array in bufmgr.c */ - size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + if (shmem_segment == BUFFER_IOCV_SHMEM_SEGMENT) + { + /* size of I/O condition variables */ + size = add_size(size, mul_size(NBuffers, + sizeof(ConditionVariableMinimallyPadded))); + /* to allow aligning the above */ + size = add_size(size, PG_CACHE_LINE_SIZE); + } + + if (shmem_segment == CHECKPOINT_BUFFERS_SHMEM_SEGMENT) + { + /* size of checkpoint sort array in bufmgr.c */ + size = add_size(size, mul_size(NBuffers, sizeof(CkptSortItem))); + } return size; } diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c index a50955d5286..a9952b36eba 100644 --- a/src/backend/storage/buffer/buf_table.c +++ b/src/backend/storage/buffer/buf_table.c @@ -22,6 +22,7 @@ #include "postgres.h" #include "storage/buf_internals.h" +#include "storage/pg_shmem.h" /* entry for buffer lookup hashtable */ typedef struct @@ -59,10 +60,11 @@ InitBufTable(int size) info.entrysize = sizeof(BufferLookupEnt); info.num_partitions = NUM_BUFFER_PARTITIONS; - SharedBufHash = ShmemInitHash("Shared Buffer Lookup Table", + SharedBufHash = ShmemInitHashInSegment("Shared Buffer Lookup Table", size, size, &info, - HASH_ELEM | HASH_BLOBS | HASH_PARTITION); + HASH_ELEM | HASH_BLOBS | HASH_PARTITION, + STRATEGY_SHMEM_SEGMENT); } /* diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c index 01909be0272..bd390f2709d 100644 --- a/src/backend/storage/buffer/freelist.c +++ b/src/backend/storage/buffer/freelist.c @@ -19,6 +19,7 @@ #include "port/atomics.h" #include "storage/buf_internals.h" #include "storage/bufmgr.h" +#include "storage/pg_shmem.h" #include "storage/proc.h" #define INT_ACCESS_ONCE(var) ((int)(*((volatile int *)&(var)))) @@ -491,9 +492,9 @@ StrategyInitialize(bool init) * Get or create the shared strategy control block */ StrategyControl = (BufferStrategyControl *) - ShmemInitStruct("Buffer Strategy Status", + ShmemInitStructInSegment("Buffer Strategy Status", sizeof(BufferStrategyControl), - &found); + &found, STRATEGY_SHMEM_SEGMENT); if (!found) { diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index b60f7ef9ce2..2dbd81afc87 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -113,7 +113,7 @@ CalculateShmemSize(int *num_semaphores, int shmem_segment) sizeof(ShmemIndexEnt))); size = add_size(size, dsm_estimate_size()); size = add_size(size, DSMRegistryShmemSize()); - size = add_size(size, BufferManagerShmemSize()); + size = add_size(size, BufferManagerShmemSize(shmem_segment)); size = add_size(size, LockManagerShmemSize()); size = add_size(size, PredicateLockShmemSize()); size = add_size(size, ProcGlobalShmemSize()); diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 41fdc1e7693..edac9db6a12 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -318,7 +318,7 @@ extern void EvictRelUnpinnedBuffers(Relation rel, /* in buf_init.c */ extern void BufferManagerShmemInit(void); -extern Size BufferManagerShmemSize(void); +extern Size BufferManagerShmemSize(int); /* in localbuf.c */ extern void AtProcExit_LocalBuffers(void); diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h index 79b0b1ef9eb..a7b275b4db9 100644 --- a/src/include/storage/pg_shmem.h +++ b/src/include/storage/pg_shmem.h @@ -52,7 +52,7 @@ typedef struct ShmemSegment } ShmemSegment; /* Number of available segments for anonymous memory mappings */ -#define ANON_MAPPINGS 1 +#define ANON_MAPPINGS 6 extern PGDLLIMPORT ShmemSegment Segments[ANON_MAPPINGS]; @@ -109,7 +109,29 @@ extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags, int *memfd_flags); void PrepareHugePages(void); +/* + * To be able to dynamically resize largest parts of the data stored in shared + * memory, we split it into multiple shared memory mappings segments. Each + * segment contains only certain part of the data, which size depends on + * NBuffers. + */ + /* The main segment, contains everything except buffer blocks and related data. */ #define MAIN_SHMEM_SEGMENT 0 +/* Buffer blocks */ +#define BUFFERS_SHMEM_SEGMENT 1 + +/* Buffer descriptors */ +#define BUFFER_DESCRIPTORS_SHMEM_SEGMENT 2 + +/* Condition variables for buffers */ +#define BUFFER_IOCV_SHMEM_SEGMENT 3 + +/* Checkpoint BufferIds */ +#define CHECKPOINT_BUFFERS_SHMEM_SEGMENT 4 + +/* Buffer strategy status */ +#define STRATEGY_SHMEM_SEGMENT 5 + #endif /* PG_SHMEM_H */ -- 2.49.0 --bwrlgp6w2ubxykjq Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="v5-0007-Allow-to-resize-shared-memory-without-restart.patch" ^ permalink raw reply [nested|flat] 319+ messages in thread
end of thread, other threads:[~2025-06-17 09:22 UTC | newest] Thread overview: 319+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2024-01-22 09:45 [PATCH v13 6/8] Row pattern recognition patch (docs). Tatsuo Ishii <ishii@postgresql.org> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov 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<9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-02-24 19:08 [PATCH v2 3/6] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-03-15 15:38 [PATCH v4 3/8] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com> 2025-06-17 09:22 [PATCH v5 06/10] Introduce multiple shmem segments for shared buffers Dmitrii Dolgov <9erthalion6@gmail.com>
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