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* [PATCH v25 1/4] Add REPACK command
@ 2025-07-26 17:57 Álvaro Herrera <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Álvaro Herrera @ 2025-07-26 17:57 UTC (permalink / raw)
REPACK absorbs the functionality of VACUUM FULL and CLUSTER in a single
command. Because this functionality is completely different from
regular VACUUM, having it separate from VACUUM makes it easier for users
to understand; as for CLUSTER, the term is heavily overloaded in the
IT world and even in Postgres itself, so it's good that we can avoid it.
This also adds pg_repackdb, a new utility that can invoke the new
commands. This is heavily based on vacuumdb.
Author: Antonin Houska <[email protected]>
Co-authored-by: Álvaro Herrera <[email protected]>
Reviewed-by: Mihail Nikalayeu <[email protected]>
Reviewed-by: Robert Treat <[email protected]>
Reviewed-by: Euler Taveira <[email protected]>
Reviewed-by: Matheus Alcantara <[email protected]>
Reviewed-by: Junwang Zhao <[email protected]>
Reviewed-by: jian he <[email protected]>
Discussion: https://postgr.es/m/82651.1720540558@antos
Discussion: https://postgr.es/m/[email protected]
---
doc/src/sgml/monitoring.sgml | 223 +++++-
doc/src/sgml/ref/allfiles.sgml | 2 +
doc/src/sgml/ref/cluster.sgml | 97 +--
doc/src/sgml/ref/clusterdb.sgml | 5 +
doc/src/sgml/ref/pg_repackdb.sgml | 488 +++++++++++++
doc/src/sgml/ref/repack.sgml | 319 +++++++++
doc/src/sgml/ref/vacuum.sgml | 33 +-
doc/src/sgml/reference.sgml | 2 +
src/backend/access/heap/heapam_handler.c | 32 +-
src/backend/catalog/index.c | 2 +-
src/backend/catalog/system_views.sql | 29 +-
src/backend/commands/cluster.c | 854 +++++++++++++++--------
src/backend/commands/vacuum.c | 6 +-
src/backend/parser/gram.y | 97 ++-
src/backend/tcop/utility.c | 20 +-
src/backend/utils/adt/pgstatfuncs.c | 2 +
src/bin/psql/tab-complete.in.c | 33 +-
src/bin/scripts/Makefile | 4 +-
src/bin/scripts/meson.build | 2 +
src/bin/scripts/pg_repackdb.c | 242 +++++++
src/bin/scripts/t/103_repackdb.pl | 47 ++
src/bin/scripts/vacuuming.c | 114 ++-
src/bin/scripts/vacuuming.h | 3 +
src/include/commands/cluster.h | 8 +-
src/include/commands/progress.h | 48 +-
src/include/nodes/parsenodes.h | 35 +-
src/include/parser/kwlist.h | 1 +
src/include/tcop/cmdtaglist.h | 1 +
src/include/utils/backend_progress.h | 1 +
src/test/regress/expected/cluster.out | 134 +++-
src/test/regress/expected/rules.out | 72 +-
src/test/regress/sql/cluster.sql | 70 +-
src/tools/pgindent/typedefs.list | 2 +
33 files changed, 2483 insertions(+), 545 deletions(-)
create mode 100644 doc/src/sgml/ref/pg_repackdb.sgml
create mode 100644 doc/src/sgml/ref/repack.sgml
create mode 100644 src/bin/scripts/pg_repackdb.c
create mode 100644 src/bin/scripts/t/103_repackdb.pl
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index f3bf527d5b4..467e081f015 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -405,6 +405,14 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
</entry>
</row>
+ <row>
+ <entry><structname>pg_stat_progress_repack</structname><indexterm><primary>pg_stat_progress_repack</primary></indexterm></entry>
+ <entry>One row for each backend running
+ <command>REPACK</command>, showing current progress. See
+ <xref linkend="repack-progress-reporting"/>.
+ </entry>
+ </row>
+
<row>
<entry><structname>pg_stat_progress_basebackup</structname><indexterm><primary>pg_stat_progress_basebackup</primary></indexterm></entry>
<entry>One row for each WAL sender process streaming a base backup,
@@ -5575,7 +5583,8 @@ FROM pg_stat_get_backend_idset() AS backendid;
certain commands during command execution. Currently, the only commands
which support progress reporting are <command>ANALYZE</command>,
<command>CLUSTER</command>,
- <command>CREATE INDEX</command>, <command>VACUUM</command>,
+ <command>CREATE INDEX</command>, <command>REPACK</command>,
+ <command>VACUUM</command>,
<command>COPY</command>,
and <xref linkend="protocol-replication-base-backup"/> (i.e., replication
command that <xref linkend="app-pgbasebackup"/> issues to take
@@ -6034,6 +6043,218 @@ FROM pg_stat_get_backend_idset() AS backendid;
</table>
</sect2>
+ <sect2 id="repack-progress-reporting">
+ <title>REPACK Progress Reporting</title>
+
+ <indexterm>
+ <primary>pg_stat_progress_repack</primary>
+ </indexterm>
+
+ <para>
+ Whenever <command>REPACK</command> is running,
+ the <structname>pg_stat_progress_repack</structname> view will contain a
+ row for each backend that is currently running the command. The tables
+ below describe the information that will be reported and provide
+ information about how to interpret it.
+ </para>
+
+ <table id="pg-stat-progress-repack-view" xreflabel="pg_stat_progress_repack">
+ <title><structname>pg_stat_progress_repack</structname> View</title>
+ <tgroup cols="1">
+ <thead>
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ Column Type
+ </para>
+ <para>
+ Description
+ </para></entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>pid</structfield> <type>integer</type>
+ </para>
+ <para>
+ Process ID of backend.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>datid</structfield> <type>oid</type>
+ </para>
+ <para>
+ OID of the database to which this backend is connected.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>datname</structfield> <type>name</type>
+ </para>
+ <para>
+ Name of the database to which this backend is connected.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>relid</structfield> <type>oid</type>
+ </para>
+ <para>
+ OID of the table being repacked.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>phase</structfield> <type>text</type>
+ </para>
+ <para>
+ Current processing phase. See <xref linkend="repack-phases"/>.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>repack_index_relid</structfield> <type>oid</type>
+ </para>
+ <para>
+ If the table is being scanned using an index, this is the OID of the
+ index being used; otherwise, it is zero.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>heap_tuples_scanned</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of heap tuples scanned.
+ This counter only advances when the phase is
+ <literal>seq scanning heap</literal>,
+ <literal>index scanning heap</literal>
+ or <literal>writing new heap</literal>.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>heap_tuples_written</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of heap tuples written.
+ This counter only advances when the phase is
+ <literal>seq scanning heap</literal>,
+ <literal>index scanning heap</literal>
+ or <literal>writing new heap</literal>.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>heap_blks_total</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Total number of heap blocks in the table. This number is reported
+ as of the beginning of <literal>seq scanning heap</literal>.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>heap_blks_scanned</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of heap blocks scanned. This counter only advances when the
+ phase is <literal>seq scanning heap</literal>.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry"><para role="column_definition">
+ <structfield>index_rebuild_count</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of indexes rebuilt. This counter only advances when the phase
+ is <literal>rebuilding index</literal>.
+ </para></entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table id="repack-phases">
+ <title>REPACK Phases</title>
+ <tgroup cols="2">
+ <colspec colname="col1" colwidth="1*"/>
+ <colspec colname="col2" colwidth="2*"/>
+ <thead>
+ <row>
+ <entry>Phase</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry><literal>initializing</literal></entry>
+ <entry>
+ The command is preparing to begin scanning the heap. This phase is
+ expected to be very brief.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>seq scanning heap</literal></entry>
+ <entry>
+ The command is currently scanning the table using a sequential scan.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>index scanning heap</literal></entry>
+ <entry>
+ <command>REPACK</command> is currently scanning the table using an index scan.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>sorting tuples</literal></entry>
+ <entry>
+ <command>REPACK</command> is currently sorting tuples.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>writing new heap</literal></entry>
+ <entry>
+ <command>REPACK</command> is currently writing the new heap.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>swapping relation files</literal></entry>
+ <entry>
+ The command is currently swapping newly-built files into place.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>rebuilding index</literal></entry>
+ <entry>
+ The command is currently rebuilding an index.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>performing final cleanup</literal></entry>
+ <entry>
+ The command is performing final cleanup. When this phase is
+ completed, <command>REPACK</command> will end.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect2>
+
<sect2 id="copy-progress-reporting">
<title>COPY Progress Reporting</title>
diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index f5be638867a..eabf92e3536 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -167,6 +167,7 @@ Complete list of usable sgml source files in this directory.
<!ENTITY refreshMaterializedView SYSTEM "refresh_materialized_view.sgml">
<!ENTITY reindex SYSTEM "reindex.sgml">
<!ENTITY releaseSavepoint SYSTEM "release_savepoint.sgml">
+<!ENTITY repack SYSTEM "repack.sgml">
<!ENTITY reset SYSTEM "reset.sgml">
<!ENTITY revoke SYSTEM "revoke.sgml">
<!ENTITY rollback SYSTEM "rollback.sgml">
@@ -212,6 +213,7 @@ Complete list of usable sgml source files in this directory.
<!ENTITY pgIsready SYSTEM "pg_isready.sgml">
<!ENTITY pgReceivewal SYSTEM "pg_receivewal.sgml">
<!ENTITY pgRecvlogical SYSTEM "pg_recvlogical.sgml">
+<!ENTITY pgRepackdb SYSTEM "pg_repackdb.sgml">
<!ENTITY pgResetwal SYSTEM "pg_resetwal.sgml">
<!ENTITY pgRestore SYSTEM "pg_restore.sgml">
<!ENTITY pgRewind SYSTEM "pg_rewind.sgml">
diff --git a/doc/src/sgml/ref/cluster.sgml b/doc/src/sgml/ref/cluster.sgml
index 8811f169ea0..cfcfb65e349 100644
--- a/doc/src/sgml/ref/cluster.sgml
+++ b/doc/src/sgml/ref/cluster.sgml
@@ -33,51 +33,13 @@ CLUSTER [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
<title>Description</title>
<para>
- <command>CLUSTER</command> instructs <productname>PostgreSQL</productname>
- to cluster the table specified
- by <replaceable class="parameter">table_name</replaceable>
- based on the index specified by
- <replaceable class="parameter">index_name</replaceable>. The index must
- already have been defined on
- <replaceable class="parameter">table_name</replaceable>.
+ The <command>CLUSTER</command> command is equivalent to
+ <xref linkend="sql-repack"/> with an <literal>USING INDEX</literal>
+ clause. See there for more details.
</para>
- <para>
- When a table is clustered, it is physically reordered
- based on the index information. Clustering is a one-time operation:
- when the table is subsequently updated, the changes are
- not clustered. That is, no attempt is made to store new or
- updated rows according to their index order. (If one wishes, one can
- periodically recluster by issuing the command again. Also, setting
- the table's <literal>fillfactor</literal> storage parameter to less than
- 100% can aid in preserving cluster ordering during updates, since updated
- rows are kept on the same page if enough space is available there.)
- </para>
+<!-- Do we need to describe exactly which options map to what? They seem obvious to me. -->
- <para>
- When a table is clustered, <productname>PostgreSQL</productname>
- remembers which index it was clustered by. The form
- <command>CLUSTER <replaceable class="parameter">table_name</replaceable></command>
- reclusters the table using the same index as before. You can also
- use the <literal>CLUSTER</literal> or <literal>SET WITHOUT CLUSTER</literal>
- forms of <link linkend="sql-altertable"><command>ALTER TABLE</command></link> to set the index to be used for
- future cluster operations, or to clear any previous setting.
- </para>
-
- <para>
- <command>CLUSTER</command> without a
- <replaceable class="parameter">table_name</replaceable> reclusters all the
- previously-clustered tables in the current database that the calling user
- has privileges for. This form of <command>CLUSTER</command> cannot be
- executed inside a transaction block.
- </para>
-
- <para>
- When a table is being clustered, an <literal>ACCESS
- EXCLUSIVE</literal> lock is acquired on it. This prevents any other
- database operations (both reads and writes) from operating on the
- table until the <command>CLUSTER</command> is finished.
- </para>
</refsect1>
<refsect1>
@@ -136,63 +98,12 @@ CLUSTER [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <r
on the table.
</para>
- <para>
- In cases where you are accessing single rows randomly
- within a table, the actual order of the data in the
- table is unimportant. However, if you tend to access some
- data more than others, and there is an index that groups
- them together, you will benefit from using <command>CLUSTER</command>.
- If you are requesting a range of indexed values from a table, or a
- single indexed value that has multiple rows that match,
- <command>CLUSTER</command> will help because once the index identifies the
- table page for the first row that matches, all other rows
- that match are probably already on the same table page,
- and so you save disk accesses and speed up the query.
- </para>
-
- <para>
- <command>CLUSTER</command> can re-sort the table using either an index scan
- on the specified index, or (if the index is a b-tree) a sequential
- scan followed by sorting. It will attempt to choose the method that
- will be faster, based on planner cost parameters and available statistical
- information.
- </para>
-
<para>
While <command>CLUSTER</command> is running, the <xref
linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
pg_temp</literal>.
</para>
- <para>
- When an index scan is used, a temporary copy of the table is created that
- contains the table data in the index order. Temporary copies of each
- index on the table are created as well. Therefore, you need free space on
- disk at least equal to the sum of the table size and the index sizes.
- </para>
-
- <para>
- When a sequential scan and sort is used, a temporary sort file is
- also created, so that the peak temporary space requirement is as much
- as double the table size, plus the index sizes. This method is often
- faster than the index scan method, but if the disk space requirement is
- intolerable, you can disable this choice by temporarily setting <xref
- linkend="guc-enable-sort"/> to <literal>off</literal>.
- </para>
-
- <para>
- It is advisable to set <xref linkend="guc-maintenance-work-mem"/> to
- a reasonably large value (but not more than the amount of RAM you can
- dedicate to the <command>CLUSTER</command> operation) before clustering.
- </para>
-
- <para>
- Because the planner records statistics about the ordering of
- tables, it is advisable to run <link linkend="sql-analyze"><command>ANALYZE</command></link>
- on the newly clustered table.
- Otherwise, the planner might make poor choices of query plans.
- </para>
-
<para>
Because <command>CLUSTER</command> remembers which indexes are clustered,
one can cluster the tables one wants clustered manually the first time,
diff --git a/doc/src/sgml/ref/clusterdb.sgml b/doc/src/sgml/ref/clusterdb.sgml
index 0d2051bf6f1..546c1289c31 100644
--- a/doc/src/sgml/ref/clusterdb.sgml
+++ b/doc/src/sgml/ref/clusterdb.sgml
@@ -64,6 +64,11 @@ PostgreSQL documentation
this utility and via other methods for accessing the server.
</para>
+ <para>
+ <application>clusterdb</application> has been superceded by
+ <application>pg_repackdb</application>.
+ </para>
+
</refsect1>
diff --git a/doc/src/sgml/ref/pg_repackdb.sgml b/doc/src/sgml/ref/pg_repackdb.sgml
new file mode 100644
index 00000000000..b313b54ab63
--- /dev/null
+++ b/doc/src/sgml/ref/pg_repackdb.sgml
@@ -0,0 +1,488 @@
+<!--
+doc/src/sgml/ref/pg_repackdb.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="app-pgrepackdb">
+ <indexterm zone="app-pgrepackdb">
+ <primary>pg_repackdb</primary>
+ </indexterm>
+
+ <refmeta>
+ <refentrytitle><application>pg_repackdb</application></refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo>Application</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+ <refname>pg_repackdb</refname>
+ <refpurpose>repack and analyze a <productname>PostgreSQL</productname>
+ database</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <cmdsynopsis>
+ <command>pg_repackdb</command>
+ <arg rep="repeat"><replaceable>connection-option</replaceable></arg>
+ <arg rep="repeat"><replaceable>option</replaceable></arg>
+
+ <arg choice="plain" rep="repeat">
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><option>-t</option></arg>
+ <arg choice="plain"><option>--table</option></arg>
+ </group>
+ <replaceable>table</replaceable>
+ <arg choice="opt">( <replaceable class="parameter">column</replaceable> [,...] )</arg>
+ </arg>
+ </arg>
+
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><replaceable>dbname</replaceable></arg>
+ <arg choice="plain"><option>-a</option></arg>
+ <arg choice="plain"><option>--all</option></arg>
+ </group>
+ </arg>
+ </cmdsynopsis>
+
+ <cmdsynopsis>
+ <command>pg_repackdb</command>
+ <arg rep="repeat"><replaceable>connection-option</replaceable></arg>
+ <arg rep="repeat"><replaceable>option</replaceable></arg>
+
+ <arg choice="plain" rep="repeat">
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><option>-n</option></arg>
+ <arg choice="plain"><option>--schema</option></arg>
+ </group>
+ <replaceable>schema</replaceable>
+ </arg>
+ </arg>
+
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><replaceable>dbname</replaceable></arg>
+ <arg choice="plain"><option>-a</option></arg>
+ <arg choice="plain"><option>--all</option></arg>
+ </group>
+ </arg>
+ </cmdsynopsis>
+
+ <cmdsynopsis>
+ <command>pg_repackdb</command>
+ <arg rep="repeat"><replaceable>connection-option</replaceable></arg>
+ <arg rep="repeat"><replaceable>option</replaceable></arg>
+
+ <arg choice="plain" rep="repeat">
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><option>-N</option></arg>
+ <arg choice="plain"><option>--exclude-schema</option></arg>
+ </group>
+ <replaceable>schema</replaceable>
+ </arg>
+ </arg>
+
+ <arg choice="opt">
+ <group choice="plain">
+ <arg choice="plain"><replaceable>dbname</replaceable></arg>
+ <arg choice="plain"><option>-a</option></arg>
+ <arg choice="plain"><option>--all</option></arg>
+ </group>
+ </arg>
+ </cmdsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>
+ <application>pg_repackdb</application> is a utility for repacking a
+ <productname>PostgreSQL</productname> database.
+ <application>pg_repackdb</application> will also generate internal
+ statistics used by the <productname>PostgreSQL</productname> query
+ optimizer.
+ </para>
+
+ <para>
+ <application>pg_repackdb</application> is a wrapper around the SQL
+ command <link linkend="sql-repack"><command>REPACK</command></link> There
+ is no effective difference between repacking and analyzing databases via
+ this utility and via other methods for accessing the server.
+ </para>
+ </refsect1>
+
+ <refsect1>
+ <title>Options</title>
+
+ <para>
+ <application>pg_repackdb</application> accepts the following command-line arguments:
+ <variablelist>
+ <varlistentry>
+ <term><option>-a</option></term>
+ <term><option>--all</option></term>
+ <listitem>
+ <para>
+ Repack all databases.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option><optional>-d</optional> <replaceable class="parameter">dbname</replaceable></option></term>
+ <term><option><optional>--dbname=</optional><replaceable class="parameter">dbname</replaceable></option></term>
+ <listitem>
+ <para>
+ Specifies the name of the database to be repacked or analyzed,
+ when <option>-a</option>/<option>--all</option> is not used. If this
+ is not specified, the database name is read from the environment
+ variable <envar>PGDATABASE</envar>. If that is not set, the user name
+ specified for the connection is used.
+ The <replaceable>dbname</replaceable> can be
+ a <link linkend="libpq-connstring">connection string</link>. If so,
+ connection string parameters will override any conflicting command
+ line options.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-e</option></term>
+ <term><option>--echo</option></term>
+ <listitem>
+ <para>
+ Echo the commands that <application>pg_repackdb</application>
+ generates and sends to the server.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>--index<optional>=<replaceable class="parameter">index_name</replaceable></optional></option></term>
+ <listitem>
+ <para>
+ Pass the <literal>USING INDEX</literal> clause to <literal>REPACK</literal>,
+ and optionally the index name to specify.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-j <replaceable class="parameter">njobs</replaceable></option></term>
+ <term><option>--jobs=<replaceable class="parameter">njobs</replaceable></option></term>
+ <listitem>
+ <para>
+ Execute the repack or analyze commands in parallel by running
+ <replaceable class="parameter">njobs</replaceable>
+ commands simultaneously. This option may reduce the processing time
+ but it also increases the load on the database server.
+ </para>
+ <para>
+ <application>pg_repackdb</application> will open
+ <replaceable class="parameter">njobs</replaceable> connections to the
+ database, so make sure your <xref linkend="guc-max-connections"/>
+ setting is high enough to accommodate all connections.
+ </para>
+ <para>
+ Note that using this mode might cause deadlock failures if certain
+ system catalogs are processed in parallel.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-n <replaceable class="parameter">schema</replaceable></option></term>
+ <term><option>--schema=<replaceable class="parameter">schema</replaceable></option></term>
+ <listitem>
+ <para>
+ Repack or analyze all tables in
+ <replaceable class="parameter">schema</replaceable> only. Multiple
+ schemas can be repacked by writing multiple <option>-n</option>
+ switches.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-N <replaceable class="parameter">schema</replaceable></option></term>
+ <term><option>--exclude-schema=<replaceable class="parameter">schema</replaceable></option></term>
+ <listitem>
+ <para>
+ Do not repack or analyze any tables in
+ <replaceable class="parameter">schema</replaceable>. Multiple schemas
+ can be excluded by writing multiple <option>-N</option> switches.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-q</option></term>
+ <term><option>--quiet</option></term>
+ <listitem>
+ <para>
+ Do not display progress messages.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-t <replaceable class="parameter">table</replaceable> [ (<replaceable class="parameter">column</replaceable> [,...]) ]</option></term>
+ <term><option>--table=<replaceable class="parameter">table</replaceable> [ (<replaceable class="parameter">column</replaceable> [,...]) ]</option></term>
+ <listitem>
+ <para>
+ Repack or analyze <replaceable class="parameter">table</replaceable>
+ only. Column names can be specified only in conjunction with
+ the <option>--analyze</option> option. Multiple tables can be
+ repacked by writing multiple
+ <option>-t</option> switches.
+ </para>
+ <tip>
+ <para>
+ If you specify columns, you probably have to escape the parentheses
+ from the shell. (See examples below.)
+ </para>
+ </tip>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-v</option></term>
+ <term><option>--verbose</option></term>
+ <listitem>
+ <para>
+ Print detailed information during processing.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-V</option></term>
+ <term><option>--version</option></term>
+ <listitem>
+ <para>
+ Print the <application>pg_repackdb</application> version and exit.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-z</option></term>
+ <term><option>--analyze</option></term>
+ <listitem>
+ <para>
+ Also calculate statistics for use by the optimizer. If a column name
+ list is given, only compute statistics for those columns.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-?</option></term>
+ <term><option>--help</option></term>
+ <listitem>
+ <para>
+ Show help about <application>pg_repackdb</application> command line
+ arguments, and exit.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </para>
+
+ <para>
+ <application>pg_repackdb</application> also accepts
+ the following command-line arguments for connection parameters:
+ <variablelist>
+ <varlistentry>
+ <term><option>-h <replaceable class="parameter">host</replaceable></option></term>
+ <term><option>--host=<replaceable class="parameter">host</replaceable></option></term>
+ <listitem>
+ <para>
+ Specifies the host name of the machine on which the server
+ is running. If the value begins with a slash, it is used
+ as the directory for the Unix domain socket.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-p <replaceable class="parameter">port</replaceable></option></term>
+ <term><option>--port=<replaceable class="parameter">port</replaceable></option></term>
+ <listitem>
+ <para>
+ Specifies the TCP port or local Unix domain socket file
+ extension on which the server
+ is listening for connections.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-U <replaceable class="parameter">username</replaceable></option></term>
+ <term><option>--username=<replaceable class="parameter">username</replaceable></option></term>
+ <listitem>
+ <para>
+ User name to connect as.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-w</option></term>
+ <term><option>--no-password</option></term>
+ <listitem>
+ <para>
+ Never issue a password prompt. If the server requires
+ password authentication and a password is not available by
+ other means such as a <filename>.pgpass</filename> file, the
+ connection attempt will fail. This option can be useful in
+ batch jobs and scripts where no user is present to enter a
+ password.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-W</option></term>
+ <term><option>--password</option></term>
+ <listitem>
+ <para>
+ Force <application>pg_repackdb</application> to prompt for a
+ password before connecting to a database.
+ </para>
+
+ <para>
+ This option is never essential, since
+ <application>pg_repackdb</application> will automatically prompt
+ for a password if the server demands password authentication.
+ However, <application>pg_repackdb</application> will waste a
+ connection attempt finding out that the server wants a password.
+ In some cases it is worth typing <option>-W</option> to avoid the extra
+ connection attempt.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>--maintenance-db=<replaceable class="parameter">dbname</replaceable></option></term>
+ <listitem>
+ <para>
+ When the <option>-a</option>/<option>--all</option> is used, connect
+ to this database to gather the list of databases to repack.
+ If not specified, the <literal>postgres</literal> database will be used,
+ or if that does not exist, <literal>template1</literal> will be used.
+ This can be a <link linkend="libpq-connstring">connection
+ string</link>. If so, connection string parameters will override any
+ conflicting command line options. Also, connection string parameters
+ other than the database name itself will be re-used when connecting
+ to other databases.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </refsect1>
+
+
+ <refsect1>
+ <title>Environment</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><envar>PGDATABASE</envar></term>
+ <term><envar>PGHOST</envar></term>
+ <term><envar>PGPORT</envar></term>
+ <term><envar>PGUSER</envar></term>
+
+ <listitem>
+ <para>
+ Default connection parameters
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><envar>PG_COLOR</envar></term>
+ <listitem>
+ <para>
+ Specifies whether to use color in diagnostic messages. Possible values
+ are <literal>always</literal>, <literal>auto</literal> and
+ <literal>never</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>
+ This utility, like most other <productname>PostgreSQL</productname> utilities,
+ also uses the environment variables supported by <application>libpq</application>
+ (see <xref linkend="libpq-envars"/>).
+ </para>
+
+ </refsect1>
+
+
+ <refsect1>
+ <title>Diagnostics</title>
+
+ <para>
+ In case of difficulty, see
+ <xref linkend="sql-repack"/> and <xref linkend="app-psql"/> for
+ discussions of potential problems and error messages.
+ The database server must be running at the
+ targeted host. Also, any default connection settings and environment
+ variables used by the <application>libpq</application> front-end
+ library will apply.
+ </para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <para>
+ To repack the database <literal>test</literal>:
+<screen>
+<prompt>$ </prompt><userinput>pg_repackdb test</userinput>
+</screen>
+ </para>
+
+ <para>
+ To repack and analyze for the optimizer a database named
+ <literal>bigdb</literal>:
+<screen>
+<prompt>$ </prompt><userinput>pg_repackdb --analyze bigdb</userinput>
+</screen>
+ </para>
+
+ <para>
+ To repack a single table
+ <literal>foo</literal> in a database named
+ <literal>xyzzy</literal>, and analyze a single column
+ <literal>bar</literal> of the table for the optimizer:
+<screen>
+<prompt>$ </prompt><userinput>pg_repackdb --analyze --verbose --table='foo(bar)' xyzzy</userinput>
+</screen></para>
+
+ <para>
+ To repack all tables in the <literal>foo</literal> and <literal>bar</literal> schemas
+ in a database named <literal>xyzzy</literal>:
+<screen>
+<prompt>$ </prompt><userinput>pg_repackdb --schema='foo' --schema='bar' xyzzy</userinput>
+</screen></para>
+
+
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+
+ <simplelist type="inline">
+ <member><xref linkend="sql-repack"/></member>
+ </simplelist>
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/ref/repack.sgml b/doc/src/sgml/ref/repack.sgml
new file mode 100644
index 00000000000..0e1116eae85
--- /dev/null
+++ b/doc/src/sgml/ref/repack.sgml
@@ -0,0 +1,319 @@
+<!--
+doc/src/sgml/ref/repack.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="sql-repack">
+ <indexterm zone="sql-repack">
+ <primary>REPACK</primary>
+ </indexterm>
+
+ <refmeta>
+ <refentrytitle>REPACK</refentrytitle>
+ <manvolnum>7</manvolnum>
+ <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+ <refname>REPACK</refname>
+ <refpurpose>rewrite a table to reclaim disk space</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+REPACK [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <replaceable class="parameter">table_and_columns</replaceable> [ USING INDEX [ <replaceable class="parameter">index_name</replaceable> ] ] ]
+
+<phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>
+
+ VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
+ ANALYZE [ <replaceable class="parameter">boolean</replaceable> ]
+
+<phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
+
+ <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>
+ <command>REPACK</command> reclaims storage occupied by dead
+ tuples. Unlike <command>VACUUM</command>, it does so by rewriting the
+ entire contents of the table specified
+ by <replaceable class="parameter">table_name</replaceable> into a new disk
+ file with no extra space (except for the space guaranteed by
+ the <literal>fillfactor</literal> storage parameter), allowing unused space
+ to be returned to the operating system.
+ </para>
+
+ <para>
+ Without
+ a <replaceable class="parameter">table_name</replaceable>, <command>REPACK</command>
+ processes every table and materialized view in the current database that
+ the current user has the <literal>MAINTAIN</literal> privilege on. This
+ form of <command>REPACK</command> cannot be executed inside a transaction
+ block.
+ </para>
+
+ <para>
+ If a <literal>USING INDEX</literal> clause is specified, the rows are
+ physically reordered based on information from an index. Please see the
+ notes on clustering below.
+ </para>
+
+ <para>
+ When a table is being repacked, an <literal>ACCESS EXCLUSIVE</literal> lock
+ is acquired on it. This prevents any other database operations (both reads
+ and writes) from operating on the table until the <command>REPACK</command>
+ is finished.
+ </para>
+
+ <refsect2 id="sql-repack-notes-on-clustering" xreflabel="Notes on Clustering">
+ <title>Notes on Clustering</title>
+
+ <para>
+ If the <literal>USING INDEX</literal> clause is specified, the rows in
+ the table are physically reordered following an index: if an index name
+ is specified in the command, then that index is used; if no index name
+ is specified, then the index that has been configured as the index to
+ cluster on. If no index has been configured in this way, an error is
+ thrown. The index given in the <literal>USING INDEX</literal> clause
+ is configured as the index to cluster on, as well as an index given
+ to the <command>CLUSTER</command> command. An index can be set
+ manually using <command>ALTER TABLE ... CLUSTER ON</command>, and reset
+ with <command>ALTER TABLE ... SET WITHOUT CLUSTER</command>.
+ </para>
+
+ <para>
+ If no table name is specified in <command>REPACK USING INDEX</command>,
+ all tables which have a clustering index defined and which the calling
+ user has privileges for are processed.
+ </para>
+
+ <para>
+ Clustering is a one-time operation: when the table is
+ subsequently updated, the changes are not clustered. That is, no attempt
+ is made to store new or updated rows according to their index order. (If
+ one wishes, one can periodically recluster by issuing the command again.
+ Also, setting the table's <literal>fillfactor</literal> storage parameter
+ to less than 100% can aid in preserving cluster ordering during updates,
+ since updated rows are kept on the same page if enough space is available
+ there.)
+ </para>
+
+ <para>
+ In cases where you are accessing single rows randomly within a table, the
+ actual order of the data in the table is unimportant. However, if you tend
+ to access some data more than others, and there is an index that groups
+ them together, you will benefit from using clustering. If
+ you are requesting a range of indexed values from a table, or a single
+ indexed value that has multiple rows that match,
+ <command>REPACK</command> will help because once the index identifies the
+ table page for the first row that matches, all other rows that match are
+ probably already on the same table page, and so you save disk accesses and
+ speed up the query.
+ </para>
+
+ <para>
+ <command>REPACK</command> can re-sort the table using either an index scan
+ on the specified index (if the index is a b-tree), or a sequential scan
+ followed by sorting. It will attempt to choose the method that will be
+ faster, based on planner cost parameters and available statistical
+ information.
+ </para>
+
+ <para>
+ Because the planner records statistics about the ordering of tables, it is
+ advisable to
+ run <link linkend="sql-analyze"><command>ANALYZE</command></link> on the
+ newly repacked table. Otherwise, the planner might make poor choices of
+ query plans.
+ </para>
+ </refsect2>
+
+ <refsect2 id="sql-repack-notes-on-resources" xreflabel="Notes on Resources">
+ <title>Notes on Resources</title>
+
+ <para>
+ When an index scan or a sequential scan without sort is used, a temporary
+ copy of the table is created that contains the table data in the index
+ order. Temporary copies of each index on the table are created as well.
+ Therefore, you need free space on disk at least equal to the sum of the
+ table size and the index sizes.
+ </para>
+
+ <para>
+ When a sequential scan and sort is used, a temporary sort file is also
+ created, so that the peak temporary space requirement is as much as double
+ the table size, plus the index sizes. This method is often faster than
+ the index scan method, but if the disk space requirement is intolerable,
+ you can disable this choice by temporarily setting
+ <xref linkend="guc-enable-sort"/> to <literal>off</literal>.
+ </para>
+
+ <para>
+ It is advisable to set <xref linkend="guc-maintenance-work-mem"/> to a
+ reasonably large value (but not more than the amount of RAM you can
+ dedicate to the <command>REPACK</command> operation) before repacking.
+ </para>
+ </refsect2>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Parameters</title>
+
+ <variablelist>
+ <varlistentry>
+ <term><replaceable class="parameter">table_name</replaceable></term>
+ <listitem>
+ <para>
+ The name (possibly schema-qualified) of a table.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">column_name</replaceable></term>
+ <listitem>
+ <para>
+ The name of a specific column to analyze. Defaults to all columns.
+ If a column list is specific, <literal>ANALYZE</literal> must also
+ be specified.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">index_name</replaceable></term>
+ <listitem>
+ <para>
+ The name of an index.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>VERBOSE</literal></term>
+ <listitem>
+ <para>
+ Prints a progress report as each table is repacked
+ at <literal>INFO</literal> level.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>ANALYZE</literal></term>
+ <term><literal>ANALYSE</literal></term>
+ <listitem>
+ <para>
+ Applies <xref linkend="sql-analyze"/> on the table after repacking. This is
+ currently only supported when a single (non-partitioned) table is specified.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><replaceable class="parameter">boolean</replaceable></term>
+ <listitem>
+ <para>
+ Specifies whether the selected option should be turned on or off.
+ You can write <literal>TRUE</literal>, <literal>ON</literal>, or
+ <literal>1</literal> to enable the option, and <literal>FALSE</literal>,
+ <literal>OFF</literal>, or <literal>0</literal> to disable it. The
+ <replaceable class="parameter">boolean</replaceable> value can also
+ be omitted, in which case <literal>TRUE</literal> is assumed.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>
+ To repack a table, one must have the <literal>MAINTAIN</literal> privilege
+ on the table.
+ </para>
+
+ <para>
+ While <command>REPACK</command> is running, the <xref
+ linkend="guc-search-path"/> is temporarily changed to <literal>pg_catalog,
+ pg_temp</literal>.
+ </para>
+
+ <para>
+ Each backend running <command>REPACK</command> will report its progress
+ in the <structname>pg_stat_progress_repack</structname> view. See
+ <xref linkend="repack-progress-reporting"/> for details.
+ </para>
+
+ <para>
+ Repacking a partitioned table repacks each of its partitions. If an index
+ is specified, each partition is repacked using the partition of that
+ index. <command>REPACK</command> on a partitioned table cannot be executed
+ inside a transaction block.
+ </para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <para>
+ Repack the table <literal>employees</literal>:
+<programlisting>
+REPACK employees;
+</programlisting>
+ </para>
+
+ <para>
+ Repack the table <literal>employees</literal> on the basis of its
+ index <literal>employees_ind</literal> (Since index is used here, this is
+ effectively clustering):
+<programlisting>
+REPACK employees USING INDEX employees_ind;
+</programlisting>
+ </para>
+
+ <para>
+ Repack the table <literal>cases</literal> on physical ordering,
+ running an <command>ANALYZE</command> on the given columns once
+ repacking is done, showing informational messages:
+<programlisting>
+REPACK (ANALYZE, VERBOSE) cases (district, case_nr);
+</programlisting>
+ </para>
+
+ <para>
+ Repack all tables in the database on which you have
+ the <literal>MAINTAIN</literal> privilege:
+<programlisting>
+REPACK;
+</programlisting>
+ </para>
+
+ <para>
+ Repack all tables for which a clustering index has previously been
+ configured on which you have the <literal>MAINTAIN</literal> privilege,
+ showing informational messages:
+<programlisting>
+REPACK (VERBOSE) USING INDEX;
+</programlisting>
+ </para>
+
+ </refsect1>
+
+ <refsect1>
+ <title>Compatibility</title>
+
+ <para>
+ There is no <command>REPACK</command> statement in the SQL standard.
+ </para>
+
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/ref/vacuum.sgml b/doc/src/sgml/ref/vacuum.sgml
index bd5dcaf86a5..062b658cfcd 100644
--- a/doc/src/sgml/ref/vacuum.sgml
+++ b/doc/src/sgml/ref/vacuum.sgml
@@ -25,7 +25,6 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
<phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>
- FULL [ <replaceable class="parameter">boolean</replaceable> ]
FREEZE [ <replaceable class="parameter">boolean</replaceable> ]
VERBOSE [ <replaceable class="parameter">boolean</replaceable> ]
ANALYZE [ <replaceable class="parameter">boolean</replaceable> ]
@@ -39,6 +38,7 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
SKIP_DATABASE_STATS [ <replaceable class="parameter">boolean</replaceable> ]
ONLY_DATABASE_STATS [ <replaceable class="parameter">boolean</replaceable> ]
BUFFER_USAGE_LIMIT <replaceable class="parameter">size</replaceable>
+ FULL [ <replaceable class="parameter">boolean</replaceable> ]
<phrase>and <replaceable class="parameter">table_and_columns</replaceable> is:</phrase>
@@ -95,20 +95,6 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
<title>Parameters</title>
<variablelist>
- <varlistentry>
- <term><literal>FULL</literal></term>
- <listitem>
- <para>
- Selects <quote>full</quote> vacuum, which can reclaim more
- space, but takes much longer and exclusively locks the table.
- This method also requires extra disk space, since it writes a
- new copy of the table and doesn't release the old copy until
- the operation is complete. Usually this should only be used when a
- significant amount of space needs to be reclaimed from within the table.
- </para>
- </listitem>
- </varlistentry>
-
<varlistentry>
<term><literal>FREEZE</literal></term>
<listitem>
@@ -362,6 +348,23 @@ VACUUM [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] [ <re
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><literal>FULL</literal></term>
+ <listitem>
+ <para>
+ This option, which is deprecated, makes <command>VACUUM</command>
+ behave like <command>REPACK</command> without a
+ <literal>USING INDEX</literal> clause.
+ This method of compacting the table takes much longer than
+ <command>VACUUM</command> and exclusively locks the table.
+ This method also requires extra disk space, since it writes a
+ new copy of the table and doesn't release the old copy until
+ the operation is complete. Usually this should only be used when a
+ significant amount of space needs to be reclaimed from within the table.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><replaceable class="parameter">boolean</replaceable></term>
<listitem>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index ff85ace83fc..2ee08e21f41 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -195,6 +195,7 @@
&refreshMaterializedView;
&reindex;
&releaseSavepoint;
+ &repack;
&reset;
&revoke;
&rollback;
@@ -257,6 +258,7 @@
&pgIsready;
&pgReceivewal;
&pgRecvlogical;
+ &pgRepackdb;
&pgRestore;
&pgVerifyBackup;
&psqlRef;
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index bcbac844bb6..79f9de5d760 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -741,13 +741,13 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
if (OldIndex != NULL && !use_sort)
{
const int ci_index[] = {
- PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_INDEX_RELID
+ PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_INDEX_RELID
};
int64 ci_val[2];
/* Set phase and OIDOldIndex to columns */
- ci_val[0] = PROGRESS_CLUSTER_PHASE_INDEX_SCAN_HEAP;
+ ci_val[0] = PROGRESS_REPACK_PHASE_INDEX_SCAN_HEAP;
ci_val[1] = RelationGetRelid(OldIndex);
pgstat_progress_update_multi_param(2, ci_index, ci_val);
@@ -759,15 +759,15 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
else
{
/* In scan-and-sort mode and also VACUUM FULL, set phase */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_SEQ_SCAN_HEAP);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_SEQ_SCAN_HEAP);
tableScan = table_beginscan(OldHeap, SnapshotAny, 0, (ScanKey) NULL);
heapScan = (HeapScanDesc) tableScan;
indexScan = NULL;
/* Set total heap blocks */
- pgstat_progress_update_param(PROGRESS_CLUSTER_TOTAL_HEAP_BLKS,
+ pgstat_progress_update_param(PROGRESS_REPACK_TOTAL_HEAP_BLKS,
heapScan->rs_nblocks);
}
@@ -809,7 +809,7 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
* is manually updated to the correct value when the table
* scan finishes.
*/
- pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_BLKS_SCANNED,
+ pgstat_progress_update_param(PROGRESS_REPACK_HEAP_BLKS_SCANNED,
heapScan->rs_nblocks);
break;
}
@@ -825,7 +825,7 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
*/
if (prev_cblock != heapScan->rs_cblock)
{
- pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_BLKS_SCANNED,
+ pgstat_progress_update_param(PROGRESS_REPACK_HEAP_BLKS_SCANNED,
(heapScan->rs_cblock +
heapScan->rs_nblocks -
heapScan->rs_startblock
@@ -912,14 +912,14 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
* In scan-and-sort mode, report increase in number of tuples
* scanned
*/
- pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_TUPLES_SCANNED,
+ pgstat_progress_update_param(PROGRESS_REPACK_HEAP_TUPLES_SCANNED,
*num_tuples);
}
else
{
const int ct_index[] = {
- PROGRESS_CLUSTER_HEAP_TUPLES_SCANNED,
- PROGRESS_CLUSTER_HEAP_TUPLES_WRITTEN
+ PROGRESS_REPACK_HEAP_TUPLES_SCANNED,
+ PROGRESS_REPACK_HEAP_TUPLES_WRITTEN
};
int64 ct_val[2];
@@ -952,14 +952,14 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
double n_tuples = 0;
/* Report that we are now sorting tuples */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_SORT_TUPLES);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_SORT_TUPLES);
tuplesort_performsort(tuplesort);
/* Report that we are now writing new heap */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_WRITE_NEW_HEAP);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_WRITE_NEW_HEAP);
for (;;)
{
@@ -977,7 +977,7 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
values, isnull,
rwstate);
/* Report n_tuples */
- pgstat_progress_update_param(PROGRESS_CLUSTER_HEAP_TUPLES_WRITTEN,
+ pgstat_progress_update_param(PROGRESS_REPACK_HEAP_TUPLES_WRITTEN,
n_tuples);
}
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 5d9db167e59..08d4b8e44d7 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -4079,7 +4079,7 @@ reindex_relation(const ReindexStmt *stmt, Oid relid, int flags,
Assert(!ReindexIsProcessingIndex(indexOid));
/* Set index rebuild count */
- pgstat_progress_update_param(PROGRESS_CLUSTER_INDEX_REBUILD_COUNT,
+ pgstat_progress_update_param(PROGRESS_REPACK_INDEX_REBUILD_COUNT,
i);
i++;
}
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index dec8df4f8ee..1ad30116631 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1269,14 +1269,15 @@ CREATE VIEW pg_stat_progress_vacuum AS
FROM pg_stat_get_progress_info('VACUUM') AS S
LEFT JOIN pg_database D ON S.datid = D.oid;
-CREATE VIEW pg_stat_progress_cluster AS
+CREATE VIEW pg_stat_progress_repack AS
SELECT
S.pid AS pid,
S.datid AS datid,
D.datname AS datname,
S.relid AS relid,
CASE S.param1 WHEN 1 THEN 'CLUSTER'
- WHEN 2 THEN 'VACUUM FULL'
+ WHEN 2 THEN 'REPACK'
+ WHEN 3 THEN 'VACUUM FULL'
END AS command,
CASE S.param2 WHEN 0 THEN 'initializing'
WHEN 1 THEN 'seq scanning heap'
@@ -1287,15 +1288,35 @@ CREATE VIEW pg_stat_progress_cluster AS
WHEN 6 THEN 'rebuilding index'
WHEN 7 THEN 'performing final cleanup'
END AS phase,
- CAST(S.param3 AS oid) AS cluster_index_relid,
+ CAST(S.param3 AS oid) AS repack_index_relid,
S.param4 AS heap_tuples_scanned,
S.param5 AS heap_tuples_written,
S.param6 AS heap_blks_total,
S.param7 AS heap_blks_scanned,
S.param8 AS index_rebuild_count
- FROM pg_stat_get_progress_info('CLUSTER') AS S
+ FROM pg_stat_get_progress_info('REPACK') AS S
LEFT JOIN pg_database D ON S.datid = D.oid;
+-- This view is as the one above, except for renaming a column and avoiding
+-- 'REPACK' as a command name to report.
+CREATE VIEW pg_stat_progress_cluster AS
+ SELECT
+ pid,
+ datid,
+ datname,
+ relid,
+ CASE WHEN command IN ('CLUSTER', 'VACUUM FULL') THEN command
+ WHEN repack_index_relid = 0 THEN 'VACUUM FULL'
+ ELSE 'CLUSTER' END AS command,
+ phase,
+ repack_index_relid AS cluster_index_relid,
+ heap_tuples_scanned,
+ heap_tuples_written,
+ heap_blks_total,
+ heap_blks_scanned,
+ index_rebuild_count
+ FROM pg_stat_progress_repack;
+
CREATE VIEW pg_stat_progress_create_index AS
SELECT
S.pid AS pid, S.datid AS datid, D.datname AS datname,
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index b55221d44cd..18bee52a4ee 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -67,27 +67,36 @@ typedef struct
Oid indexOid;
} RelToCluster;
-
-static void cluster_multiple_rels(List *rtcs, ClusterParams *params);
-static void rebuild_relation(Relation OldHeap, Relation index, bool verbose);
+static bool cluster_rel_recheck(RepackCommand cmd, Relation OldHeap,
+ Oid indexOid, Oid userid, int options);
+static void rebuild_relation(RepackCommand cmd,
+ Relation OldHeap, Relation index, bool verbose);
static void copy_table_data(Relation NewHeap, Relation OldHeap, Relation OldIndex,
bool verbose, bool *pSwapToastByContent,
TransactionId *pFreezeXid, MultiXactId *pCutoffMulti);
-static List *get_tables_to_cluster(MemoryContext cluster_context);
-static List *get_tables_to_cluster_partitioned(MemoryContext cluster_context,
- Oid indexOid);
-static bool cluster_is_permitted_for_relation(Oid relid, Oid userid);
+static List *get_tables_to_repack(RepackCommand cmd, bool usingindex,
+ MemoryContext permcxt);
+static List *get_tables_to_repack_partitioned(RepackCommand cmd,
+ Oid relid, bool rel_is_index,
+ MemoryContext permcxt);
+static bool cluster_is_permitted_for_relation(RepackCommand cmd,
+ Oid relid, Oid userid);
+static Relation process_single_relation(RepackStmt *stmt,
+ ClusterParams *params);
+static Oid determine_clustered_index(Relation rel, bool usingindex,
+ const char *indexname);
+static const char *RepackCommandAsString(RepackCommand cmd);
-/*---------------------------------------------------------------------------
- * This cluster code allows for clustering multiple tables at once. Because
+/*
+ * The repack code allows for processing multiple tables at once. Because
* of this, we cannot just run everything on a single transaction, or we
* would be forced to acquire exclusive locks on all the tables being
* clustered, simultaneously --- very likely leading to deadlock.
*
- * To solve this we follow a similar strategy to VACUUM code,
- * clustering each relation in a separate transaction. For this to work,
- * we need to:
+ * To solve this we follow a similar strategy to VACUUM code, processing each
+ * relation in a separate transaction. For this to work, we need to:
+ *
* - provide a separate memory context so that we can pass information in
* a way that survives across transactions
* - start a new transaction every time a new relation is clustered
@@ -98,197 +107,165 @@ static bool cluster_is_permitted_for_relation(Oid relid, Oid userid);
*
* The single-relation case does not have any such overhead.
*
- * We also allow a relation to be specified without index. In that case,
- * the indisclustered bit will be looked up, and an ERROR will be thrown
- * if there is no index with the bit set.
- *---------------------------------------------------------------------------
+ * We also allow a relation to be repacked following an index, but without
+ * naming a specific one. In that case, the indisclustered bit will be
+ * looked up, and an ERROR will be thrown if no so-marked index is found.
*/
void
-cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel)
+ExecRepack(ParseState *pstate, RepackStmt *stmt, bool isTopLevel)
{
- ListCell *lc;
ClusterParams params = {0};
- bool verbose = false;
Relation rel = NULL;
- Oid indexOid = InvalidOid;
- MemoryContext cluster_context;
+ MemoryContext repack_context;
List *rtcs;
/* Parse option list */
- foreach(lc, stmt->params)
+ foreach_node(DefElem, opt, stmt->params)
{
- DefElem *opt = (DefElem *) lfirst(lc);
-
if (strcmp(opt->defname, "verbose") == 0)
- verbose = defGetBoolean(opt);
+ params.options |= defGetBoolean(opt) ? CLUOPT_VERBOSE : 0;
+ else if (strcmp(opt->defname, "analyze") == 0 ||
+ strcmp(opt->defname, "analyse") == 0)
+ params.options |= defGetBoolean(opt) ? CLUOPT_ANALYZE : 0;
else
ereport(ERROR,
- (errcode(ERRCODE_SYNTAX_ERROR),
- errmsg("unrecognized CLUSTER option \"%s\"",
- opt->defname),
- parser_errposition(pstate, opt->location)));
+ errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("unrecognized %s option \"%s\"",
+ RepackCommandAsString(stmt->command),
+ opt->defname),
+ parser_errposition(pstate, opt->location));
}
- params.options = (verbose ? CLUOPT_VERBOSE : 0);
-
+ /*
+ * If a single relation is specified, process it and we're done ... unless
+ * the relation is a partitioned table, in which case we fall through.
+ */
if (stmt->relation != NULL)
{
- /* This is the single-relation case. */
- Oid tableOid;
-
- /*
- * Find, lock, and check permissions on the table. We obtain
- * AccessExclusiveLock right away to avoid lock-upgrade hazard in the
- * single-transaction case.
- */
- tableOid = RangeVarGetRelidExtended(stmt->relation,
- AccessExclusiveLock,
- 0,
- RangeVarCallbackMaintainsTable,
- NULL);
- rel = table_open(tableOid, NoLock);
-
- /*
- * Reject clustering a remote temp table ... their local buffer
- * manager is not going to cope.
- */
- if (RELATION_IS_OTHER_TEMP(rel))
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot cluster temporary tables of other sessions")));
-
- if (stmt->indexname == NULL)
- {
- ListCell *index;
-
- /* We need to find the index that has indisclustered set. */
- foreach(index, RelationGetIndexList(rel))
- {
- indexOid = lfirst_oid(index);
- if (get_index_isclustered(indexOid))
- break;
- indexOid = InvalidOid;
- }
-
- if (!OidIsValid(indexOid))
- ereport(ERROR,
- (errcode(ERRCODE_UNDEFINED_OBJECT),
- errmsg("there is no previously clustered index for table \"%s\"",
- stmt->relation->relname)));
- }
- else
- {
- /*
- * The index is expected to be in the same namespace as the
- * relation.
- */
- indexOid = get_relname_relid(stmt->indexname,
- rel->rd_rel->relnamespace);
- if (!OidIsValid(indexOid))
- ereport(ERROR,
- (errcode(ERRCODE_UNDEFINED_OBJECT),
- errmsg("index \"%s\" for table \"%s\" does not exist",
- stmt->indexname, stmt->relation->relname)));
- }
-
- /* For non-partitioned tables, do what we came here to do. */
- if (rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
- {
- cluster_rel(rel, indexOid, ¶ms);
- /* cluster_rel closes the relation, but keeps lock */
-
- return;
- }
+ rel = process_single_relation(stmt, ¶ms);
+ if (rel == NULL)
+ return; /* all done */
}
+ /*
+ * Don't allow ANALYZE in the multiple-relation case for now. Maybe we
+ * can add support for this later.
+ */
+ if (params.options & CLUOPT_ANALYZE)
+ ereport(ERROR,
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot %s multiple tables", "REPACK (ANALYZE)"));
+
/*
* By here, we know we are in a multi-table situation. In order to avoid
* holding locks for too long, we want to process each table in its own
* transaction. This forces us to disallow running inside a user
* transaction block.
*/
- PreventInTransactionBlock(isTopLevel, "CLUSTER");
+ PreventInTransactionBlock(isTopLevel, RepackCommandAsString(stmt->command));
/* Also, we need a memory context to hold our list of relations */
- cluster_context = AllocSetContextCreate(PortalContext,
- "Cluster",
- ALLOCSET_DEFAULT_SIZES);
+ repack_context = AllocSetContextCreate(PortalContext,
+ "Repack",
+ ALLOCSET_DEFAULT_SIZES);
+
+ params.options |= CLUOPT_RECHECK;
/*
- * Either we're processing a partitioned table, or we were not given any
- * table name at all. In either case, obtain a list of relations to
- * process.
- *
- * In the former case, an index name must have been given, so we don't
- * need to recheck its "indisclustered" bit, but we have to check that it
- * is an index that we can cluster on. In the latter case, we set the
- * option bit to have indisclustered verified.
- *
- * Rechecking the relation itself is necessary here in all cases.
+ * If we don't have a relation yet, determine a relation list. If we do,
+ * then it must be a partitioned table, and we want to process its
+ * partitions.
*/
- params.options |= CLUOPT_RECHECK;
- if (rel != NULL)
+ if (rel == NULL)
{
- Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
- check_index_is_clusterable(rel, indexOid, AccessShareLock);
- rtcs = get_tables_to_cluster_partitioned(cluster_context, indexOid);
-
- /* close relation, releasing lock on parent table */
- table_close(rel, AccessExclusiveLock);
+ Assert(stmt->indexname == NULL);
+ rtcs = get_tables_to_repack(stmt->command, stmt->usingindex,
+ repack_context);
}
else
{
- rtcs = get_tables_to_cluster(cluster_context);
- params.options |= CLUOPT_RECHECK_ISCLUSTERED;
+ Oid relid;
+ bool rel_is_index;
+
+ Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
+
+ /*
+ * If USING INDEX was specified, resolve the index name now and pass
+ * it down.
+ */
+ if (stmt->usingindex)
+ {
+ /*
+ * If no index name was specified when repacking a partitioned
+ * table, punt for now. Maybe we can improve this later.
+ */
+ if (!stmt->indexname)
+ ereport(ERROR,
+ errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("there is no previously clustered index for table \"%s\"",
+ RelationGetRelationName(rel)));
+
+ relid = determine_clustered_index(rel, stmt->usingindex,
+ stmt->indexname);
+ if (!OidIsValid(relid))
+ elog(ERROR, "unable to determine index to cluster on");
+ /* XXX is this the right place for this check? */
+ check_index_is_clusterable(rel, relid, AccessExclusiveLock);
+ rel_is_index = true;
+ }
+ else
+ {
+ relid = RelationGetRelid(rel);
+ rel_is_index = false;
+ }
+
+ rtcs = get_tables_to_repack_partitioned(stmt->command,
+ relid, rel_is_index,
+ repack_context);
+
+ /* close parent relation, releasing lock on it */
+ table_close(rel, AccessExclusiveLock);
+ rel = NULL;
}
- /* Do the job. */
- cluster_multiple_rels(rtcs, ¶ms);
-
- /* Start a new transaction for the cleanup work. */
- StartTransactionCommand();
-
- /* Clean up working storage */
- MemoryContextDelete(cluster_context);
-}
-
-/*
- * Given a list of relations to cluster, process each of them in a separate
- * transaction.
- *
- * We expect to be in a transaction at start, but there isn't one when we
- * return.
- */
-static void
-cluster_multiple_rels(List *rtcs, ClusterParams *params)
-{
- ListCell *lc;
-
/* Commit to get out of starting transaction */
PopActiveSnapshot();
CommitTransactionCommand();
/* Cluster the tables, each in a separate transaction */
- foreach(lc, rtcs)
+ Assert(rel == NULL);
+ foreach_ptr(RelToCluster, rtc, rtcs)
{
- RelToCluster *rtc = (RelToCluster *) lfirst(lc);
- Relation rel;
-
/* Start a new transaction for each relation. */
StartTransactionCommand();
+ /*
+ * Open the target table, coping with the case where it has been
+ * dropped.
+ */
+ rel = try_table_open(rtc->tableOid, AccessExclusiveLock);
+ if (rel == NULL)
+ {
+ CommitTransactionCommand();
+ continue;
+ }
+
/* functions in indexes may want a snapshot set */
PushActiveSnapshot(GetTransactionSnapshot());
- rel = table_open(rtc->tableOid, AccessExclusiveLock);
-
/* Process this table */
- cluster_rel(rel, rtc->indexOid, params);
+ cluster_rel(stmt->command, rel, rtc->indexOid, ¶ms);
/* cluster_rel closes the relation, but keeps lock */
PopActiveSnapshot();
CommitTransactionCommand();
}
+
+ /* Start a new transaction for the cleanup work. */
+ StartTransactionCommand();
+
+ /* Clean up working storage */
+ MemoryContextDelete(repack_context);
}
/*
@@ -304,11 +281,14 @@ cluster_multiple_rels(List *rtcs, ClusterParams *params)
* them incrementally while we load the table.
*
* If indexOid is InvalidOid, the table will be rewritten in physical order
- * instead of index order. This is the new implementation of VACUUM FULL,
- * and error messages should refer to the operation as VACUUM not CLUSTER.
+ * instead of index order.
+ *
+ * 'cmd' indicates which command is being executed, to be used for error
+ * messages.
*/
void
-cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params)
+cluster_rel(RepackCommand cmd, Relation OldHeap, Oid indexOid,
+ ClusterParams *params)
{
Oid tableOid = RelationGetRelid(OldHeap);
Oid save_userid;
@@ -323,13 +303,8 @@ cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params)
/* Check for user-requested abort. */
CHECK_FOR_INTERRUPTS();
- pgstat_progress_start_command(PROGRESS_COMMAND_CLUSTER, tableOid);
- if (OidIsValid(indexOid))
- pgstat_progress_update_param(PROGRESS_CLUSTER_COMMAND,
- PROGRESS_CLUSTER_COMMAND_CLUSTER);
- else
- pgstat_progress_update_param(PROGRESS_CLUSTER_COMMAND,
- PROGRESS_CLUSTER_COMMAND_VACUUM_FULL);
+ pgstat_progress_start_command(PROGRESS_COMMAND_REPACK, tableOid);
+ pgstat_progress_update_param(PROGRESS_REPACK_COMMAND, cmd);
/*
* Switch to the table owner's userid, so that any index functions are run
@@ -350,86 +325,38 @@ cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params)
* *must* skip the one on indisclustered since it would reject an attempt
* to cluster a not-previously-clustered index.
*/
- if (recheck)
- {
- /* Check that the user still has privileges for the relation */
- if (!cluster_is_permitted_for_relation(tableOid, save_userid))
- {
- relation_close(OldHeap, AccessExclusiveLock);
- goto out;
- }
-
- /*
- * Silently skip a temp table for a remote session. Only doing this
- * check in the "recheck" case is appropriate (which currently means
- * somebody is executing a database-wide CLUSTER or on a partitioned
- * table), because there is another check in cluster() which will stop
- * any attempt to cluster remote temp tables by name. There is
- * another check in cluster_rel which is redundant, but we leave it
- * for extra safety.
- */
- if (RELATION_IS_OTHER_TEMP(OldHeap))
- {
- relation_close(OldHeap, AccessExclusiveLock);
- goto out;
- }
-
- if (OidIsValid(indexOid))
- {
- /*
- * Check that the index still exists
- */
- if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(indexOid)))
- {
- relation_close(OldHeap, AccessExclusiveLock);
- goto out;
- }
-
- /*
- * Check that the index is still the one with indisclustered set,
- * if needed.
- */
- if ((params->options & CLUOPT_RECHECK_ISCLUSTERED) != 0 &&
- !get_index_isclustered(indexOid))
- {
- relation_close(OldHeap, AccessExclusiveLock);
- goto out;
- }
- }
- }
+ if (recheck &&
+ !cluster_rel_recheck(cmd, OldHeap, indexOid, save_userid,
+ params->options))
+ goto out;
/*
- * We allow VACUUM FULL, but not CLUSTER, on shared catalogs. CLUSTER
- * would work in most respects, but the index would only get marked as
- * indisclustered in the current database, leading to unexpected behavior
- * if CLUSTER were later invoked in another database.
+ * We allow repacking shared catalogs only when not using an index. It
+ * would work to use an index in most respects, but the index would only
+ * get marked as indisclustered in the current database, leading to
+ * unexpected behavior if CLUSTER were later invoked in another database.
*/
if (OidIsValid(indexOid) && OldHeap->rd_rel->relisshared)
ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot cluster a shared catalog")));
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot run %s on a shared catalog",
+ RepackCommandAsString(cmd)));
/*
* Don't process temp tables of other backends ... their local buffer
* manager is not going to cope.
*/
if (RELATION_IS_OTHER_TEMP(OldHeap))
- {
- if (OidIsValid(indexOid))
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot cluster temporary tables of other sessions")));
- else
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot vacuum temporary tables of other sessions")));
- }
+ ereport(ERROR,
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot run %s on temporary tables of other sessions",
+ RepackCommandAsString(cmd)));
/*
* Also check for active uses of the relation in the current transaction,
* including open scans and pending AFTER trigger events.
*/
- CheckTableNotInUse(OldHeap, OidIsValid(indexOid) ? "CLUSTER" : "VACUUM");
+ CheckTableNotInUse(OldHeap, RepackCommandAsString(cmd));
/* Check heap and index are valid to cluster on */
if (OidIsValid(indexOid))
@@ -442,6 +369,24 @@ cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params)
else
index = NULL;
+ /*
+ * When allow_system_table_mods is turned off, we disallow repacking a
+ * catalog on a particular index unless that's already the clustered index
+ * for that catalog.
+ *
+ * XXX We don't check for this in CLUSTER, because it's historically been
+ * allowed.
+ */
+ if (cmd != REPACK_COMMAND_CLUSTER &&
+ !allowSystemTableMods && OidIsValid(indexOid) &&
+ IsCatalogRelation(OldHeap) && !index->rd_index->indisclustered)
+ ereport(ERROR,
+ errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ errmsg("permission denied: \"%s\" is a system catalog",
+ RelationGetRelationName(OldHeap)),
+ errdetail("System catalogs can only be clustered by the index they're already clustered on, if any, unless \"%s\" is enabled.",
+ "allow_system_table_mods"));
+
/*
* Quietly ignore the request if this is a materialized view which has not
* been populated from its query. No harm is done because there is no data
@@ -469,7 +414,7 @@ cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params)
TransferPredicateLocksToHeapRelation(OldHeap);
/* rebuild_relation does all the dirty work */
- rebuild_relation(OldHeap, index, verbose);
+ rebuild_relation(cmd, OldHeap, index, verbose);
/* rebuild_relation closes OldHeap, and index if valid */
out:
@@ -482,6 +427,63 @@ out:
pgstat_progress_end_command();
}
+/*
+ * Check if the table (and its index) still meets the requirements of
+ * cluster_rel().
+ */
+static bool
+cluster_rel_recheck(RepackCommand cmd, Relation OldHeap, Oid indexOid,
+ Oid userid, int options)
+{
+ Oid tableOid = RelationGetRelid(OldHeap);
+
+ /* Check that the user still has privileges for the relation */
+ if (!cluster_is_permitted_for_relation(cmd, tableOid, userid))
+ {
+ relation_close(OldHeap, AccessExclusiveLock);
+ return false;
+ }
+
+ /*
+ * Silently skip a temp table for a remote session. Only doing this check
+ * in the "recheck" case is appropriate (which currently means somebody is
+ * executing a database-wide CLUSTER or on a partitioned table), because
+ * there is another check in cluster() which will stop any attempt to
+ * cluster remote temp tables by name. There is another check in
+ * cluster_rel which is redundant, but we leave it for extra safety.
+ */
+ if (RELATION_IS_OTHER_TEMP(OldHeap))
+ {
+ relation_close(OldHeap, AccessExclusiveLock);
+ return false;
+ }
+
+ if (OidIsValid(indexOid))
+ {
+ /*
+ * Check that the index still exists
+ */
+ if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(indexOid)))
+ {
+ relation_close(OldHeap, AccessExclusiveLock);
+ return false;
+ }
+
+ /*
+ * Check that the index is still the one with indisclustered set, if
+ * needed.
+ */
+ if ((options & CLUOPT_RECHECK_ISCLUSTERED) != 0 &&
+ !get_index_isclustered(indexOid))
+ {
+ relation_close(OldHeap, AccessExclusiveLock);
+ return false;
+ }
+ }
+
+ return true;
+}
+
/*
* Verify that the specified heap and index are valid to cluster on
*
@@ -626,7 +628,8 @@ mark_index_clustered(Relation rel, Oid indexOid, bool is_internal)
* On exit, they are closed, but locks on them are not released.
*/
static void
-rebuild_relation(Relation OldHeap, Relation index, bool verbose)
+rebuild_relation(RepackCommand cmd,
+ Relation OldHeap, Relation index, bool verbose)
{
Oid tableOid = RelationGetRelid(OldHeap);
Oid accessMethod = OldHeap->rd_rel->relam;
@@ -642,8 +645,8 @@ rebuild_relation(Relation OldHeap, Relation index, bool verbose)
Assert(CheckRelationLockedByMe(OldHeap, AccessExclusiveLock, false) &&
(index == NULL || CheckRelationLockedByMe(index, AccessExclusiveLock, false)));
- if (index)
- /* Mark the correct index as clustered */
+ /* for CLUSTER or REPACK USING INDEX, mark the index as the one to use */
+ if (index != NULL)
mark_index_clustered(OldHeap, RelationGetRelid(index), true);
/* Remember info about rel before closing OldHeap */
@@ -958,20 +961,20 @@ copy_table_data(Relation NewHeap, Relation OldHeap, Relation OldIndex, bool verb
/* Log what we're doing */
if (OldIndex != NULL && !use_sort)
ereport(elevel,
- (errmsg("clustering \"%s.%s\" using index scan on \"%s\"",
- nspname,
- RelationGetRelationName(OldHeap),
- RelationGetRelationName(OldIndex))));
+ errmsg("repacking \"%s.%s\" using index scan on \"%s\"",
+ nspname,
+ RelationGetRelationName(OldHeap),
+ RelationGetRelationName(OldIndex)));
else if (use_sort)
ereport(elevel,
- (errmsg("clustering \"%s.%s\" using sequential scan and sort",
- nspname,
- RelationGetRelationName(OldHeap))));
+ errmsg("repacking \"%s.%s\" using sequential scan and sort",
+ nspname,
+ RelationGetRelationName(OldHeap)));
else
ereport(elevel,
- (errmsg("vacuuming \"%s.%s\"",
- nspname,
- RelationGetRelationName(OldHeap))));
+ errmsg("repacking \"%s.%s\" in physical order",
+ nspname,
+ RelationGetRelationName(OldHeap)));
/*
* Hand off the actual copying to AM specific function, the generic code
@@ -1458,8 +1461,8 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
int i;
/* Report that we are now swapping relation files */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_SWAP_REL_FILES);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_SWAP_REL_FILES);
/* Zero out possible results from swapped_relation_files */
memset(mapped_tables, 0, sizeof(mapped_tables));
@@ -1509,14 +1512,14 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
reindex_flags |= REINDEX_REL_FORCE_INDEXES_PERMANENT;
/* Report that we are now reindexing relations */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_REBUILD_INDEX);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_REBUILD_INDEX);
reindex_relation(NULL, OIDOldHeap, reindex_flags, &reindex_params);
/* Report that we are now doing clean up */
- pgstat_progress_update_param(PROGRESS_CLUSTER_PHASE,
- PROGRESS_CLUSTER_PHASE_FINAL_CLEANUP);
+ pgstat_progress_update_param(PROGRESS_REPACK_PHASE,
+ PROGRESS_REPACK_PHASE_FINAL_CLEANUP);
/*
* If the relation being rebuilt is pg_class, swap_relation_files()
@@ -1632,106 +1635,191 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
}
}
-
/*
- * Get a list of tables that the current user has privileges on and
- * have indisclustered set. Return the list in a List * of RelToCluster
- * (stored in the specified memory context), each one giving the tableOid
- * and the indexOid on which the table is already clustered.
+ * Determine which relations to process, when REPACK/CLUSTER is called
+ * without specifying a table name. The exact process depends on whether
+ * USING INDEX was given or not, and in any case we only return tables and
+ * materialized views that the current user has privileges to repack/cluster.
+ *
+ * If USING INDEX was given, we scan pg_index to find those that have
+ * indisclustered set; if it was not given, scan pg_class and return all
+ * tables.
+ *
+ * Return it as a list of RelToCluster in the given memory context.
*/
static List *
-get_tables_to_cluster(MemoryContext cluster_context)
+get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt)
{
- Relation indRelation;
+ Relation catalog;
TableScanDesc scan;
- ScanKeyData entry;
- HeapTuple indexTuple;
- Form_pg_index index;
- MemoryContext old_context;
+ HeapTuple tuple;
List *rtcs = NIL;
- /*
- * Get all indexes that have indisclustered set and that the current user
- * has the appropriate privileges for.
- */
- indRelation = table_open(IndexRelationId, AccessShareLock);
- ScanKeyInit(&entry,
- Anum_pg_index_indisclustered,
- BTEqualStrategyNumber, F_BOOLEQ,
- BoolGetDatum(true));
- scan = table_beginscan_catalog(indRelation, 1, &entry);
- while ((indexTuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+ if (usingindex)
{
- RelToCluster *rtc;
+ ScanKeyData entry;
- index = (Form_pg_index) GETSTRUCT(indexTuple);
+ catalog = table_open(IndexRelationId, AccessShareLock);
+ ScanKeyInit(&entry,
+ Anum_pg_index_indisclustered,
+ BTEqualStrategyNumber, F_BOOLEQ,
+ BoolGetDatum(true));
+ scan = table_beginscan_catalog(catalog, 1, &entry);
+ while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+ {
+ RelToCluster *rtc;
+ Form_pg_index index;
+ MemoryContext oldcxt;
- if (!cluster_is_permitted_for_relation(index->indrelid, GetUserId()))
- continue;
+ index = (Form_pg_index) GETSTRUCT(tuple);
- /* Use a permanent memory context for the result list */
- old_context = MemoryContextSwitchTo(cluster_context);
+ /*
+ * Try to obtain a light lock on the index's table, to ensure it
+ * doesn't go away while we collect the list. If we cannot, just
+ * disregard it.
+ */
+ if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock))
+ continue;
- rtc = (RelToCluster *) palloc(sizeof(RelToCluster));
- rtc->tableOid = index->indrelid;
- rtc->indexOid = index->indexrelid;
- rtcs = lappend(rtcs, rtc);
+ /* Verify that the table still exists */
+ if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(index->indrelid)))
+ {
+ /* Release useless lock */
+ UnlockRelationOid(index->indrelid, AccessShareLock);
+ continue;
+ }
- MemoryContextSwitchTo(old_context);
+ if (!cluster_is_permitted_for_relation(cmd, index->indrelid,
+ GetUserId()))
+ continue;
+
+ /* Use a permanent memory context for the result list */
+ oldcxt = MemoryContextSwitchTo(permcxt);
+ rtc = palloc(sizeof(RelToCluster));
+ rtc->tableOid = index->indrelid;
+ rtc->indexOid = index->indexrelid;
+ rtcs = lappend(rtcs, rtc);
+ MemoryContextSwitchTo(oldcxt);
+ }
}
- table_endscan(scan);
+ else
+ {
+ catalog = table_open(RelationRelationId, AccessShareLock);
+ scan = table_beginscan_catalog(catalog, 0, NULL);
- relation_close(indRelation, AccessShareLock);
+ while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+ {
+ RelToCluster *rtc;
+ Form_pg_class class;
+ MemoryContext oldcxt;
+
+ class = (Form_pg_class) GETSTRUCT(tuple);
+
+ /*
+ * Try to obtain a light lock on the table, to ensure it doesn't
+ * go away while we collect the list. If we cannot, just
+ * disregard the table.
+ */
+ if (!ConditionalLockRelationOid(class->oid, AccessShareLock))
+ continue;
+
+ /* Verify that the table still exists */
+ if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid)))
+ {
+ /* Release useless lock */
+ UnlockRelationOid(class->oid, AccessShareLock);
+ continue;
+ }
+
+ /* Can only process plain tables and matviews */
+ if (class->relkind != RELKIND_RELATION &&
+ class->relkind != RELKIND_MATVIEW)
+ continue;
+
+ /* noisily skip rels which the user can't process */
+ if (!cluster_is_permitted_for_relation(cmd, class->oid,
+ GetUserId()))
+ continue;
+
+ /* Use a permanent memory context for the result list */
+ oldcxt = MemoryContextSwitchTo(permcxt);
+ rtc = palloc(sizeof(RelToCluster));
+ rtc->tableOid = class->oid;
+ rtc->indexOid = InvalidOid;
+ rtcs = lappend(rtcs, rtc);
+ MemoryContextSwitchTo(oldcxt);
+ }
+ }
+
+ table_endscan(scan);
+ relation_close(catalog, AccessShareLock);
return rtcs;
}
/*
- * Given an index on a partitioned table, return a list of RelToCluster for
+ * Given a partitioned table or its index, return a list of RelToCluster for
* all the children leaves tables/indexes.
*
* Like expand_vacuum_rel, but here caller must hold AccessExclusiveLock
* on the table containing the index.
+ *
+ * 'rel_is_index' tells whether 'relid' is that of an index (true) or of the
+ * owning relation.
*/
static List *
-get_tables_to_cluster_partitioned(MemoryContext cluster_context, Oid indexOid)
+get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid,
+ bool rel_is_index, MemoryContext permcxt)
{
List *inhoids;
- ListCell *lc;
List *rtcs = NIL;
- MemoryContext old_context;
- /* Do not lock the children until they're processed */
- inhoids = find_all_inheritors(indexOid, NoLock, NULL);
-
- foreach(lc, inhoids)
+ /*
+ * Do not lock the children until they're processed. Note that we do hold
+ * a lock on the parent partitioned table.
+ */
+ inhoids = find_all_inheritors(relid, NoLock, NULL);
+ foreach_oid(child_oid, inhoids)
{
- Oid indexrelid = lfirst_oid(lc);
- Oid relid = IndexGetRelation(indexrelid, false);
+ Oid table_oid,
+ index_oid;
RelToCluster *rtc;
+ MemoryContext oldcxt;
- /* consider only leaf indexes */
- if (get_rel_relkind(indexrelid) != RELKIND_INDEX)
- continue;
+ if (rel_is_index)
+ {
+ /* consider only leaf indexes */
+ if (get_rel_relkind(child_oid) != RELKIND_INDEX)
+ continue;
+
+ table_oid = IndexGetRelation(child_oid, false);
+ index_oid = child_oid;
+ }
+ else
+ {
+ /* consider only leaf relations */
+ if (get_rel_relkind(child_oid) != RELKIND_RELATION)
+ continue;
+
+ table_oid = child_oid;
+ index_oid = InvalidOid;
+ }
/*
* It's possible that the user does not have privileges to CLUSTER the
- * leaf partition despite having such privileges on the partitioned
- * table. We skip any partitions which the user is not permitted to
- * CLUSTER.
+ * leaf partition despite having them on the partitioned table. Skip
+ * if so.
*/
- if (!cluster_is_permitted_for_relation(relid, GetUserId()))
+ if (!cluster_is_permitted_for_relation(cmd, table_oid, GetUserId()))
continue;
/* Use a permanent memory context for the result list */
- old_context = MemoryContextSwitchTo(cluster_context);
-
- rtc = (RelToCluster *) palloc(sizeof(RelToCluster));
- rtc->tableOid = relid;
- rtc->indexOid = indexrelid;
+ oldcxt = MemoryContextSwitchTo(permcxt);
+ rtc = palloc(sizeof(RelToCluster));
+ rtc->tableOid = table_oid;
+ rtc->indexOid = index_oid;
rtcs = lappend(rtcs, rtc);
-
- MemoryContextSwitchTo(old_context);
+ MemoryContextSwitchTo(oldcxt);
}
return rtcs;
@@ -1742,13 +1830,167 @@ get_tables_to_cluster_partitioned(MemoryContext cluster_context, Oid indexOid)
* function emits a WARNING.
*/
static bool
-cluster_is_permitted_for_relation(Oid relid, Oid userid)
+cluster_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid)
{
+ Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK);
+
if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK)
return true;
ereport(WARNING,
- (errmsg("permission denied to cluster \"%s\", skipping it",
- get_rel_name(relid))));
+ errmsg("permission denied to execute %s on \"%s\", skipping it",
+ RepackCommandAsString(cmd),
+ get_rel_name(relid)));
+
return false;
}
+
+
+/*
+ * Given a RepackStmt with an indicated relation name, resolve the relation
+ * name, obtain lock on it, then determine what to do based on the relation
+ * type: if it's table and not partitioned, repack it as indicated (using an
+ * existing clustered index, or following the given one), and return NULL.
+ *
+ * On the other hand, if the table is partitioned, do nothing further and
+ * instead return the opened and locked relcache entry, so that caller can
+ * process the partitions using the multiple-table handling code. In this
+ * case, if an index name is given, it's up to the caller to resolve it.
+ */
+static Relation
+process_single_relation(RepackStmt *stmt, ClusterParams *params)
+{
+ Relation rel;
+ Oid tableOid;
+
+ Assert(stmt->relation != NULL);
+ Assert(stmt->command == REPACK_COMMAND_CLUSTER ||
+ stmt->command == REPACK_COMMAND_REPACK);
+
+ /*
+ * Find, lock, and check permissions on the table. We obtain
+ * AccessExclusiveLock right away to avoid lock-upgrade hazard in the
+ * single-transaction case.
+ */
+ tableOid = RangeVarGetRelidExtended(stmt->relation->relation,
+ AccessExclusiveLock,
+ 0,
+ RangeVarCallbackMaintainsTable,
+ NULL);
+ rel = table_open(tableOid, NoLock);
+
+ /*
+ * Reject clustering a remote temp table ... their local buffer manager is
+ * not going to cope.
+ */
+ if (RELATION_IS_OTHER_TEMP(rel))
+ ereport(ERROR,
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot execute %s on temporary tables of other sessions",
+ RepackCommandAsString(stmt->command)));
+
+ /*
+ * Make sure ANALYZE is specified if a column list is present.
+ */
+ if ((params->options & CLUOPT_ANALYZE) == 0 && stmt->relation->va_cols != NIL)
+ ereport(ERROR,
+ errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("ANALYZE option must be specified when a column list is provided"));
+
+ /*
+ * For partitioned tables, let caller handle this. Otherwise, process it
+ * here and we're done.
+ */
+ if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+ return rel;
+ else
+ {
+ Oid indexOid;
+
+ indexOid = determine_clustered_index(rel, stmt->usingindex,
+ stmt->indexname);
+ if (OidIsValid(indexOid))
+ check_index_is_clusterable(rel, indexOid, AccessExclusiveLock);
+ cluster_rel(stmt->command, rel, indexOid, params);
+
+ /* Do an analyze, if requested */
+ if (params->options & CLUOPT_ANALYZE)
+ {
+ VacuumParams vac_params = {0};
+
+ vac_params.options |= VACOPT_ANALYZE;
+ if (params->options & CLUOPT_VERBOSE)
+ vac_params.options |= VACOPT_VERBOSE;
+ analyze_rel(RelationGetRelid(rel), NULL, vac_params,
+ stmt->relation->va_cols, true, NULL);
+ }
+
+ return NULL;
+ }
+}
+
+/*
+ * Given a relation and the usingindex/indexname options in a
+ * REPACK USING INDEX or CLUSTER command, return the OID of the
+ * index to use for clustering the table.
+ *
+ * Caller must hold lock on the relation so that the set of indexes
+ * doesn't change, and must call check_index_is_clusterable.
+ */
+static Oid
+determine_clustered_index(Relation rel, bool usingindex, const char *indexname)
+{
+ Oid indexOid;
+
+ if (indexname == NULL && usingindex)
+ {
+ /*
+ * If USING INDEX with no name is given, find a clustered index, or
+ * error out if none.
+ */
+ indexOid = InvalidOid;
+ foreach_oid(idxoid, RelationGetIndexList(rel))
+ {
+ if (get_index_isclustered(idxoid))
+ {
+ indexOid = idxoid;
+ break;
+ }
+ }
+
+ if (!OidIsValid(indexOid))
+ ereport(ERROR,
+ errcode(ERRCODE_UNDEFINED_OBJECT),
+ errmsg("there is no previously clustered index for table \"%s\"",
+ RelationGetRelationName(rel)));
+ }
+ else if (indexname != NULL)
+ {
+ /* An index was specified; obtain its OID. */
+ indexOid = get_relname_relid(indexname, rel->rd_rel->relnamespace);
+ if (!OidIsValid(indexOid))
+ ereport(ERROR,
+ errcode(ERRCODE_UNDEFINED_OBJECT),
+ errmsg("index \"%s\" for table \"%s\" does not exist",
+ indexname, RelationGetRelationName(rel)));
+ }
+ else
+ indexOid = InvalidOid;
+
+ return indexOid;
+}
+
+static const char *
+RepackCommandAsString(RepackCommand cmd)
+{
+ switch (cmd)
+ {
+ case REPACK_COMMAND_REPACK:
+ return "REPACK";
+ case REPACK_COMMAND_VACUUMFULL:
+ return "VACUUM";
+ case REPACK_COMMAND_CLUSTER:
+ return "CLUSTER";
+ }
+ return "???";
+}
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index ed03e3bd50d..62207ceff7e 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -348,7 +348,6 @@ ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel)
}
}
-
/*
* Sanity check DISABLE_PAGE_SKIPPING option.
*/
@@ -2280,8 +2279,9 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams params,
if ((params.options & VACOPT_VERBOSE) != 0)
cluster_params.options |= CLUOPT_VERBOSE;
- /* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
- cluster_rel(rel, InvalidOid, &cluster_params);
+ /* VACUUM FULL is a variant of REPACK; see cluster.c */
+ cluster_rel(REPACK_COMMAND_VACUUMFULL, rel, InvalidOid,
+ &cluster_params);
/* cluster_rel closes the relation, but keeps lock */
rel = NULL;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a4b29c822e8..c463aa1415d 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -286,7 +286,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
AlterCompositeTypeStmt AlterUserMappingStmt
AlterRoleStmt AlterRoleSetStmt AlterPolicyStmt AlterStatsStmt
AlterDefaultPrivilegesStmt DefACLAction
- AnalyzeStmt CallStmt ClosePortalStmt ClusterStmt CommentStmt
+ AnalyzeStmt CallStmt ClosePortalStmt CommentStmt
ConstraintsSetStmt CopyStmt CreateAsStmt CreateCastStmt
CreateDomainStmt CreateExtensionStmt CreateGroupStmt CreateOpClassStmt
CreateOpFamilyStmt AlterOpFamilyStmt CreatePLangStmt
@@ -303,7 +303,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
GrantStmt GrantRoleStmt ImportForeignSchemaStmt IndexStmt InsertStmt
ListenStmt LoadStmt LockStmt MergeStmt NotifyStmt ExplainableStmt PreparableStmt
CreateFunctionStmt AlterFunctionStmt ReindexStmt RemoveAggrStmt
- RemoveFuncStmt RemoveOperStmt RenameStmt ReturnStmt RevokeStmt RevokeRoleStmt
+ RemoveFuncStmt RemoveOperStmt RenameStmt RepackStmt ReturnStmt RevokeStmt RevokeRoleStmt
RuleActionStmt RuleActionStmtOrEmpty RuleStmt
SecLabelStmt SelectStmt TransactionStmt TransactionStmtLegacy TruncateStmt
UnlistenStmt UpdateStmt VacuumStmt
@@ -322,7 +322,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <str> opt_single_name
%type <list> opt_qualified_name
-%type <boolean> opt_concurrently
+%type <boolean> opt_concurrently opt_usingindex
%type <dbehavior> opt_drop_behavior
%type <list> opt_utility_option_list
%type <list> utility_option_list
@@ -770,7 +770,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
QUOTE QUOTES
RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
- REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
+ REFRESH REINDEX RELATIVE_P RELEASE RENAME REPACK REPEATABLE REPLACE REPLICA
RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
ROUTINE ROUTINES ROW ROWS RULE
@@ -1032,7 +1032,6 @@ stmt:
| CallStmt
| CheckPointStmt
| ClosePortalStmt
- | ClusterStmt
| CommentStmt
| ConstraintsSetStmt
| CopyStmt
@@ -1106,6 +1105,7 @@ stmt:
| RemoveFuncStmt
| RemoveOperStmt
| RenameStmt
+ | RepackStmt
| RevokeStmt
| RevokeRoleStmt
| RuleStmt
@@ -1142,6 +1142,11 @@ opt_concurrently:
| /*EMPTY*/ { $$ = false; }
;
+opt_usingindex:
+ USING INDEX { $$ = true; }
+ | /* EMPTY */ { $$ = false; }
+ ;
+
opt_drop_behavior:
CASCADE { $$ = DROP_CASCADE; }
| RESTRICT { $$ = DROP_RESTRICT; }
@@ -11959,38 +11964,93 @@ CreateConversionStmt:
/*****************************************************************************
*
* QUERY:
+ * REPACK [ (options) ] [ <qualified_name> [ <name_list> ] [ USING INDEX <index_name> ] ]
+ *
+ * obsolete variants:
* CLUSTER (options) [ <qualified_name> [ USING <index_name> ] ]
* CLUSTER [VERBOSE] [ <qualified_name> [ USING <index_name> ] ]
* CLUSTER [VERBOSE] <index_name> ON <qualified_name> (for pre-8.3)
*
*****************************************************************************/
-ClusterStmt:
- CLUSTER '(' utility_option_list ')' qualified_name cluster_index_specification
+RepackStmt:
+ REPACK opt_utility_option_list vacuum_relation USING INDEX name
{
- ClusterStmt *n = makeNode(ClusterStmt);
+ RepackStmt *n = makeNode(RepackStmt);
- n->relation = $5;
+ n->command = REPACK_COMMAND_REPACK;
+ n->relation = (VacuumRelation *) $3;
n->indexname = $6;
+ n->usingindex = true;
+ n->params = $2;
+ $$ = (Node *) n;
+ }
+ | REPACK opt_utility_option_list vacuum_relation opt_usingindex
+ {
+ RepackStmt *n = makeNode(RepackStmt);
+
+ n->command = REPACK_COMMAND_REPACK;
+ n->relation = (VacuumRelation *) $3;
+ n->indexname = NULL;
+ n->usingindex = $4;
+ n->params = $2;
+ $$ = (Node *) n;
+ }
+ | REPACK '(' utility_option_list ')'
+ {
+ RepackStmt *n = makeNode(RepackStmt);
+
+ n->command = REPACK_COMMAND_REPACK;
+ n->relation = NULL;
+ n->indexname = NULL;
+ n->usingindex = false;
+ n->params = $3;
+ $$ = (Node *) n;
+ }
+ | REPACK opt_usingindex
+ {
+ RepackStmt *n = makeNode(RepackStmt);
+
+ n->command = REPACK_COMMAND_REPACK;
+ n->relation = NULL;
+ n->indexname = NULL;
+ n->usingindex = $2;
+ n->params = NIL;
+ $$ = (Node *) n;
+ }
+ | CLUSTER '(' utility_option_list ')' qualified_name cluster_index_specification
+ {
+ RepackStmt *n = makeNode(RepackStmt);
+
+ n->command = REPACK_COMMAND_CLUSTER;
+ n->relation = makeNode(VacuumRelation);
+ n->relation->relation = $5;
+ n->indexname = $6;
+ n->usingindex = true;
n->params = $3;
$$ = (Node *) n;
}
| CLUSTER opt_utility_option_list
{
- ClusterStmt *n = makeNode(ClusterStmt);
+ RepackStmt *n = makeNode(RepackStmt);
+ n->command = REPACK_COMMAND_CLUSTER;
n->relation = NULL;
n->indexname = NULL;
+ n->usingindex = true;
n->params = $2;
$$ = (Node *) n;
}
/* unparenthesized VERBOSE kept for pre-14 compatibility */
| CLUSTER opt_verbose qualified_name cluster_index_specification
{
- ClusterStmt *n = makeNode(ClusterStmt);
+ RepackStmt *n = makeNode(RepackStmt);
- n->relation = $3;
+ n->command = REPACK_COMMAND_CLUSTER;
+ n->relation = makeNode(VacuumRelation);
+ n->relation->relation = $3;
n->indexname = $4;
+ n->usingindex = true;
if ($2)
n->params = list_make1(makeDefElem("verbose", NULL, @2));
$$ = (Node *) n;
@@ -11998,20 +12058,25 @@ ClusterStmt:
/* unparenthesized VERBOSE kept for pre-17 compatibility */
| CLUSTER VERBOSE
{
- ClusterStmt *n = makeNode(ClusterStmt);
+ RepackStmt *n = makeNode(RepackStmt);
+ n->command = REPACK_COMMAND_CLUSTER;
n->relation = NULL;
n->indexname = NULL;
+ n->usingindex = true;
n->params = list_make1(makeDefElem("verbose", NULL, @2));
$$ = (Node *) n;
}
/* kept for pre-8.3 compatibility */
| CLUSTER opt_verbose name ON qualified_name
{
- ClusterStmt *n = makeNode(ClusterStmt);
+ RepackStmt *n = makeNode(RepackStmt);
- n->relation = $5;
+ n->command = REPACK_COMMAND_CLUSTER;
+ n->relation = makeNode(VacuumRelation);
+ n->relation->relation = $5;
n->indexname = $3;
+ n->usingindex = true;
if ($2)
n->params = list_make1(makeDefElem("verbose", NULL, @2));
$$ = (Node *) n;
@@ -18028,6 +18093,7 @@ unreserved_keyword:
| RELATIVE_P
| RELEASE
| RENAME
+ | REPACK
| REPEATABLE
| REPLACE
| REPLICA
@@ -18661,6 +18727,7 @@ bare_label_keyword:
| RELATIVE_P
| RELEASE
| RENAME
+ | REPACK
| REPEATABLE
| REPLACE
| REPLICA
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 918db53dd5e..1295dc25d02 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -277,9 +277,9 @@ ClassifyUtilityCommandAsReadOnly(Node *parsetree)
return COMMAND_OK_IN_RECOVERY | COMMAND_OK_IN_READ_ONLY_TXN;
}
- case T_ClusterStmt:
case T_ReindexStmt:
case T_VacuumStmt:
+ case T_RepackStmt:
{
/*
* These commands write WAL, so they're not strictly
@@ -854,14 +854,14 @@ standard_ProcessUtility(PlannedStmt *pstmt,
ExecuteCallStmt(castNode(CallStmt, parsetree), params, isAtomicContext, dest);
break;
- case T_ClusterStmt:
- cluster(pstate, (ClusterStmt *) parsetree, isTopLevel);
- break;
-
case T_VacuumStmt:
ExecVacuum(pstate, (VacuumStmt *) parsetree, isTopLevel);
break;
+ case T_RepackStmt:
+ ExecRepack(pstate, (RepackStmt *) parsetree, isTopLevel);
+ break;
+
case T_ExplainStmt:
ExplainQuery(pstate, (ExplainStmt *) parsetree, params, dest);
break;
@@ -2850,10 +2850,6 @@ CreateCommandTag(Node *parsetree)
tag = CMDTAG_CALL;
break;
- case T_ClusterStmt:
- tag = CMDTAG_CLUSTER;
- break;
-
case T_VacuumStmt:
if (((VacuumStmt *) parsetree)->is_vacuumcmd)
tag = CMDTAG_VACUUM;
@@ -2861,6 +2857,10 @@ CreateCommandTag(Node *parsetree)
tag = CMDTAG_ANALYZE;
break;
+ case T_RepackStmt:
+ tag = CMDTAG_REPACK;
+ break;
+
case T_ExplainStmt:
tag = CMDTAG_EXPLAIN;
break;
@@ -3498,7 +3498,7 @@ GetCommandLogLevel(Node *parsetree)
lev = LOGSTMT_ALL;
break;
- case T_ClusterStmt:
+ case T_RepackStmt:
lev = LOGSTMT_DDL;
break;
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index a710508979e..1a7bb1e4a31 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -289,6 +289,8 @@ pg_stat_get_progress_info(PG_FUNCTION_ARGS)
cmdtype = PROGRESS_COMMAND_ANALYZE;
else if (pg_strcasecmp(cmd, "CLUSTER") == 0)
cmdtype = PROGRESS_COMMAND_CLUSTER;
+ else if (pg_strcasecmp(cmd, "REPACK") == 0)
+ cmdtype = PROGRESS_COMMAND_REPACK;
else if (pg_strcasecmp(cmd, "CREATE INDEX") == 0)
cmdtype = PROGRESS_COMMAND_CREATE_INDEX;
else if (pg_strcasecmp(cmd, "BASEBACKUP") == 0)
diff --git a/src/bin/psql/tab-complete.in.c b/src/bin/psql/tab-complete.in.c
index 36ea6a4d557..b1fe7703296 100644
--- a/src/bin/psql/tab-complete.in.c
+++ b/src/bin/psql/tab-complete.in.c
@@ -1257,7 +1257,7 @@ static const char *const sql_commands[] = {
"DELETE FROM", "DISCARD", "DO", "DROP", "END", "EXECUTE", "EXPLAIN",
"FETCH", "GRANT", "IMPORT FOREIGN SCHEMA", "INSERT INTO", "LISTEN", "LOAD", "LOCK",
"MERGE INTO", "MOVE", "NOTIFY", "PREPARE",
- "REASSIGN", "REFRESH MATERIALIZED VIEW", "REINDEX", "RELEASE",
+ "REASSIGN", "REFRESH MATERIALIZED VIEW", "REINDEX", "RELEASE", "REPACK",
"RESET", "REVOKE", "ROLLBACK",
"SAVEPOINT", "SECURITY LABEL", "SELECT", "SET", "SHOW", "START",
"TABLE", "TRUNCATE", "UNLISTEN", "UPDATE", "VACUUM", "VALUES", "WITH",
@@ -5008,6 +5008,37 @@ match_previous_words(int pattern_id,
COMPLETE_WITH_QUERY(Query_for_list_of_tablespaces);
}
+/* REPACK */
+ else if (Matches("REPACK"))
+ COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_clusterables);
+ else if (Matches("REPACK", "(*)"))
+ COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_clusterables);
+ /* If we have REPACK <sth>, then add "USING INDEX" */
+ else if (Matches("REPACK", MatchAnyExcept("(")))
+ COMPLETE_WITH("USING INDEX");
+ /* If we have REPACK (*) <sth>, then add "USING INDEX" */
+ else if (Matches("REPACK", "(*)", MatchAny))
+ COMPLETE_WITH("USING INDEX");
+ /* If we have REPACK <sth> USING, then add the index as well */
+ else if (Matches("REPACK", MatchAny, "USING", "INDEX"))
+ {
+ set_completion_reference(prev3_wd);
+ COMPLETE_WITH_SCHEMA_QUERY(Query_for_index_of_table);
+ }
+ else if (HeadMatches("REPACK", "(*") &&
+ !HeadMatches("REPACK", "(*)"))
+ {
+ /*
+ * This fires if we're in an unfinished parenthesized option list.
+ * get_previous_words treats a completed parenthesized option list as
+ * one word, so the above test is correct.
+ */
+ if (ends_with(prev_wd, '(') || ends_with(prev_wd, ','))
+ COMPLETE_WITH("VERBOSE");
+ else if (TailMatches("VERBOSE"))
+ COMPLETE_WITH("ON", "OFF");
+ }
+
/* SECURITY LABEL */
else if (Matches("SECURITY"))
COMPLETE_WITH("LABEL");
diff --git a/src/bin/scripts/Makefile b/src/bin/scripts/Makefile
index 019ca06455d..f0c1bd4175c 100644
--- a/src/bin/scripts/Makefile
+++ b/src/bin/scripts/Makefile
@@ -16,7 +16,7 @@ subdir = src/bin/scripts
top_builddir = ../../..
include $(top_builddir)/src/Makefile.global
-PROGRAMS = createdb createuser dropdb dropuser clusterdb vacuumdb reindexdb pg_isready
+PROGRAMS = createdb createuser dropdb dropuser clusterdb vacuumdb reindexdb pg_isready pg_repackdb
override CPPFLAGS := -I$(libpq_srcdir) $(CPPFLAGS)
LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport)
@@ -31,6 +31,7 @@ clusterdb: clusterdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport su
vacuumdb: vacuumdb.o vacuuming.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
reindexdb: reindexdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
pg_isready: pg_isready.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
+pg_repackdb: pg_repackdb.o vacuuming.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
install: all installdirs
$(INSTALL_PROGRAM) createdb$(X) '$(DESTDIR)$(bindir)'/createdb$(X)
@@ -41,6 +42,7 @@ install: all installdirs
$(INSTALL_PROGRAM) vacuumdb$(X) '$(DESTDIR)$(bindir)'/vacuumdb$(X)
$(INSTALL_PROGRAM) reindexdb$(X) '$(DESTDIR)$(bindir)'/reindexdb$(X)
$(INSTALL_PROGRAM) pg_isready$(X) '$(DESTDIR)$(bindir)'/pg_isready$(X)
+ $(INSTALL_PROGRAM) pg_repackdb$(X) '$(DESTDIR)$(bindir)'/pg_repackdb$(X)
installdirs:
$(MKDIR_P) '$(DESTDIR)$(bindir)'
diff --git a/src/bin/scripts/meson.build b/src/bin/scripts/meson.build
index a4fed59d1c9..be573cae682 100644
--- a/src/bin/scripts/meson.build
+++ b/src/bin/scripts/meson.build
@@ -42,6 +42,7 @@ vacuuming_common = static_library('libvacuuming_common',
binaries = [
'vacuumdb',
+ 'pg_repackdb',
]
foreach binary : binaries
binary_sources = files('@[email protected]'.format(binary))
@@ -80,6 +81,7 @@ tests += {
't/100_vacuumdb.pl',
't/101_vacuumdb_all.pl',
't/102_vacuumdb_stages.pl',
+ 't/103_repackdb.pl',
't/200_connstr.pl',
],
},
diff --git a/src/bin/scripts/pg_repackdb.c b/src/bin/scripts/pg_repackdb.c
new file mode 100644
index 00000000000..1edfa34ed0f
--- /dev/null
+++ b/src/bin/scripts/pg_repackdb.c
@@ -0,0 +1,242 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_repackdb
+ * An utility to run REPACK
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * FIXME: this is missing a way to specify the index to use to repack one
+ * table, or whether to pass a WITH INDEX clause when multiple tables are
+ * used. Something like --index[=indexname]. Adding that bleeds into
+ * vacuuming.c as well.
+ *
+ * src/bin/scripts/pg_repackdb.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <limits.h>
+
+#include "common.h"
+#include "common/logging.h"
+#include "fe_utils/option_utils.h"
+#include "vacuuming.h"
+
+static void help(const char *progname);
+static void check_objfilter(bits32 objfilter);
+
+int
+main(int argc, char *argv[])
+{
+ static struct option long_options[] = {
+ {"host", required_argument, NULL, 'h'},
+ {"port", required_argument, NULL, 'p'},
+ {"username", required_argument, NULL, 'U'},
+ {"no-password", no_argument, NULL, 'w'},
+ {"password", no_argument, NULL, 'W'},
+ {"echo", no_argument, NULL, 'e'},
+ {"quiet", no_argument, NULL, 'q'},
+ {"dbname", required_argument, NULL, 'd'},
+ {"analyze", no_argument, NULL, 'z'},
+ {"all", no_argument, NULL, 'a'},
+ /* XXX this could be 'i', but optional_arg is messy */
+ {"index", optional_argument, NULL, 1},
+ {"table", required_argument, NULL, 't'},
+ {"verbose", no_argument, NULL, 'v'},
+ {"jobs", required_argument, NULL, 'j'},
+ {"schema", required_argument, NULL, 'n'},
+ {"exclude-schema", required_argument, NULL, 'N'},
+ {"maintenance-db", required_argument, NULL, 2},
+ {NULL, 0, NULL, 0}
+ };
+
+ const char *progname;
+ int optindex;
+ int c;
+ const char *dbname = NULL;
+ const char *maintenance_db = NULL;
+ ConnParams cparams;
+ bool echo = false;
+ bool quiet = false;
+ vacuumingOptions vacopts;
+ SimpleStringList objects = {NULL, NULL};
+ int concurrentCons = 1;
+ int tbl_count = 0;
+ int ret;
+
+ /* initialize options */
+ memset(&vacopts, 0, sizeof(vacopts));
+ vacopts.mode = MODE_REPACK;
+
+ /* the same for connection parameters */
+ memset(&cparams, 0, sizeof(cparams));
+ cparams.prompt_password = TRI_DEFAULT;
+
+ pg_logging_init(argv[0]);
+ progname = get_progname(argv[0]);
+ set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pgscripts"));
+
+ handle_help_version_opts(argc, argv, progname, help);
+
+ while ((c = getopt_long(argc, argv, "ad:eh:j:n:N:p:qt:U:vwWz",
+ long_options, &optindex)) != -1)
+ {
+ switch (c)
+ {
+ case 'a':
+ vacopts.objfilter |= OBJFILTER_ALL_DBS;
+ break;
+ case 'd':
+ vacopts.objfilter |= OBJFILTER_DATABASE;
+ dbname = pg_strdup(optarg);
+ break;
+ case 'e':
+ echo = true;
+ break;
+ case 'h':
+ cparams.pghost = pg_strdup(optarg);
+ break;
+ case 'j':
+ if (!option_parse_int(optarg, "-j/--jobs", 1, INT_MAX,
+ &concurrentCons))
+ exit(1);
+ break;
+ case 'n':
+ vacopts.objfilter |= OBJFILTER_SCHEMA;
+ simple_string_list_append(&objects, optarg);
+ break;
+ case 'N':
+ vacopts.objfilter |= OBJFILTER_SCHEMA_EXCLUDE;
+ simple_string_list_append(&objects, optarg);
+ break;
+ case 'p':
+ cparams.pgport = pg_strdup(optarg);
+ break;
+ case 'q':
+ quiet = true;
+ break;
+ case 't':
+ vacopts.objfilter |= OBJFILTER_TABLE;
+ simple_string_list_append(&objects, optarg);
+ tbl_count++;
+ break;
+ case 'U':
+ cparams.pguser = pg_strdup(optarg);
+ break;
+ case 'v':
+ vacopts.verbose = true;
+ break;
+ case 'w':
+ cparams.prompt_password = TRI_NO;
+ break;
+ case 'W':
+ cparams.prompt_password = TRI_YES;
+ break;
+ case 'z':
+ vacopts.and_analyze = true;
+ break;
+ case 1:
+ vacopts.using_index = true;
+ if (optarg)
+ vacopts.indexname = pg_strdup(optarg);
+ else
+ vacopts.indexname = NULL;
+ break;
+ case 2:
+ maintenance_db = pg_strdup(optarg);
+ break;
+ default:
+ /* getopt_long already emitted a complaint */
+ pg_log_error_hint("Try \"%s --help\" for more information.", progname);
+ exit(1);
+ }
+ }
+
+ /*
+ * Non-option argument specifies database name as long as it wasn't
+ * already specified with -d / --dbname
+ */
+ if (optind < argc && dbname == NULL)
+ {
+ vacopts.objfilter |= OBJFILTER_DATABASE;
+ dbname = argv[optind];
+ optind++;
+ }
+
+ if (optind < argc)
+ {
+ pg_log_error("too many command-line arguments (first is \"%s\")",
+ argv[optind]);
+ pg_log_error_hint("Try \"%s --help\" for more information.", progname);
+ exit(1);
+ }
+
+ /*
+ * Validate the combination of filters specified in the command-line
+ * options.
+ */
+ check_objfilter(vacopts.objfilter);
+
+ ret = vacuuming_main(&cparams, dbname, maintenance_db, &vacopts,
+ &objects, tbl_count, concurrentCons,
+ progname, echo, quiet);
+ exit(ret);
+}
+
+/*
+ * Verify that the filters used at command line are compatible.
+ */
+void
+check_objfilter(bits32 objfilter)
+{
+ if ((objfilter & OBJFILTER_ALL_DBS) &&
+ (objfilter & OBJFILTER_DATABASE))
+ pg_fatal("cannot repack all databases and a specific one at the same time");
+
+ if ((objfilter & OBJFILTER_TABLE) &&
+ (objfilter & OBJFILTER_SCHEMA))
+ pg_fatal("cannot repack all tables in schema(s) and specific table(s) at the same time");
+
+ if ((objfilter & OBJFILTER_TABLE) &&
+ (objfilter & OBJFILTER_SCHEMA_EXCLUDE))
+ pg_fatal("cannot repack specific table(s) and exclude schema(s) at the same time");
+
+ if ((objfilter & OBJFILTER_SCHEMA) &&
+ (objfilter & OBJFILTER_SCHEMA_EXCLUDE))
+ pg_fatal("cannot repack all tables in schema(s) and exclude schema(s) at the same time");
+}
+
+static void
+help(const char *progname)
+{
+ printf(_("%s repacks a PostgreSQL database.\n\n"), progname);
+ printf(_("Usage:\n"));
+ printf(_(" %s [OPTION]... [DBNAME]\n"), progname);
+ printf(_("\nOptions:\n"));
+ printf(_(" -a, --all repack all databases\n"));
+ printf(_(" -d, --dbname=DBNAME database to repack\n"));
+ printf(_(" -e, --echo show the commands being sent to the server\n"));
+ printf(_(" --index[=INDEX] repack following an index\n"));
+ printf(_(" -j, --jobs=NUM use this many concurrent connections to repack\n"));
+ printf(_(" -n, --schema=SCHEMA repack tables in the specified schema(s) only\n"));
+ printf(_(" -N, --exclude-schema=SCHEMA do not repack tables in the specified schema(s)\n"));
+ printf(_(" -q, --quiet don't write any messages\n"));
+ printf(_(" -t, --table='TABLE[(COLUMNS)]' repack specific table(s) only\n"));
+ printf(_(" -v, --verbose write a lot of output\n"));
+ printf(_(" -V, --version output version information, then exit\n"));
+ printf(_(" -z, --analyze update optimizer statistics\n"));
+ printf(_(" -?, --help show this help, then exit\n"));
+ printf(_("\nConnection options:\n"));
+ printf(_(" -h, --host=HOSTNAME database server host or socket directory\n"));
+ printf(_(" -p, --port=PORT database server port\n"));
+ printf(_(" -U, --username=USERNAME user name to connect as\n"));
+ printf(_(" -w, --no-password never prompt for password\n"));
+ printf(_(" -W, --password force password prompt\n"));
+ printf(_(" --maintenance-db=DBNAME alternate maintenance database\n"));
+ printf(_("\nRead the description of the SQL command REPACK for details.\n"));
+ printf(_("\nReport bugs to <%s>.\n"), PACKAGE_BUGREPORT);
+ printf(_("%s home page: <%s>\n"), PACKAGE_NAME, PACKAGE_URL);
+}
diff --git a/src/bin/scripts/t/103_repackdb.pl b/src/bin/scripts/t/103_repackdb.pl
new file mode 100644
index 00000000000..cadce9b837c
--- /dev/null
+++ b/src/bin/scripts/t/103_repackdb.pl
@@ -0,0 +1,47 @@
+# Copyright (c) 2021-2025, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+program_help_ok('pg_repackdb');
+program_version_ok('pg_repackdb');
+program_options_handling_ok('pg_repackdb');
+
+my $node = PostgreSQL::Test::Cluster->new('main');
+$node->init;
+$node->start;
+
+$node->issues_sql_like(
+ [ 'pg_repackdb', 'postgres', '-t', 'pg_class'],
+ qr/statement: REPACK.*pg_class;/,
+ 'pg_repackdb processes a single table');
+
+$node->safe_psql('postgres', 'CREATE USER testusr;
+ GRANT CREATE ON SCHEMA public TO testusr');
+$node->safe_psql('postgres',
+ 'CREATE TABLE cluster_1 (a int primary key);
+ ALTER TABLE cluster_1 CLUSTER ON cluster_1_pkey;
+ CREATE TABLE cluster_2 (a int unique);
+ ALTER TABLE cluster_2 CLUSTER ON cluster_2_a_key;',
+ extra_params => ['-U' => 'testusr']);
+
+$node->issues_sql_like(
+ [ 'pg_repackdb', 'postgres', '-U', 'testusr' ],
+ qr/statement: REPACK.*;/,
+ 'SQL REPACK run');
+
+$node->issues_sql_like(
+ [ 'pg_repackdb', 'postgres', '--index'],
+ qr/statement: REPACK.*cluster_1 USING INDEX.*statement: REPACK.*cluster_2 USING INDEX/ms,
+ 'pg_repackdb --index chooses multiple tables');
+
+$node->issues_sql_like(
+ [ 'pg_repackdb', 'postgres', '--analyze', '-t', 'cluster_1'],
+ qr/statement: REPACK \(ANALYZE\) public.cluster_1/,
+ 'pg_repackdb --analyze works');
+
+done_testing();
diff --git a/src/bin/scripts/vacuuming.c b/src/bin/scripts/vacuuming.c
index f836f21fb03..d8d77cabe43 100644
--- a/src/bin/scripts/vacuuming.c
+++ b/src/bin/scripts/vacuuming.c
@@ -1,6 +1,6 @@
/*-------------------------------------------------------------------------
* vacuuming.c
- * Helper routines for vacuumdb
+ * Helper routines for vacuumdb and pg_repackdb
*
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
@@ -43,8 +43,8 @@ static SimpleStringList *retrieve_objects(PGconn *conn,
static void free_retrieved_objects(SimpleStringList *list);
static void prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
vacuumingOptions *vacopts, const char *table);
-static void run_vacuum_command(PGconn *conn, const char *sql, bool echo,
- const char *table);
+static void run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
+ const char *sql, bool echo, const char *table);
/*
* Executes vacuum/analyze as indicated. Returns 0 if the plan is carried
@@ -194,6 +194,14 @@ vacuum_one_database(ConnParams *cparams,
conn = connectDatabase(cparams, progname, echo, false, true);
+ if (vacopts->mode == MODE_REPACK && PQserverVersion(conn) < 190000)
+ {
+ /* XXX arguably, here we should use VACUUM FULL instead of failing */
+ PQfinish(conn);
+ pg_fatal("cannot use the \"%s\" command on server versions older than PostgreSQL %s",
+ "REPACK", "19");
+ }
+
if (vacopts->disable_page_skipping && PQserverVersion(conn) < 90600)
{
PQfinish(conn);
@@ -286,9 +294,18 @@ vacuum_one_database(ConnParams *cparams,
if (vacopts->mode == MODE_ANALYZE_IN_STAGES)
printf(_("%s: processing database \"%s\": %s\n"),
progname, PQdb(conn), _(stage_messages[stage]));
- else
+ else if (vacopts->mode == MODE_ANALYZE)
+ printf(_("%s: analyzing database \"%s\"\n"),
+ progname, PQdb(conn));
+ else if (vacopts->mode == MODE_VACUUM)
printf(_("%s: vacuuming database \"%s\"\n"),
progname, PQdb(conn));
+ else
+ {
+ Assert(vacopts->mode == MODE_REPACK);
+ printf(_("%s: repacking database \"%s\"\n"),
+ progname, PQdb(conn));
+ }
fflush(stdout);
}
@@ -383,7 +400,7 @@ vacuum_one_database(ConnParams *cparams,
* through ParallelSlotsGetIdle.
*/
ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
- run_vacuum_command(free_slot->connection, sql.data,
+ run_vacuum_command(free_slot->connection, vacopts, sql.data,
echo, tabname);
cell = cell->next;
@@ -408,7 +425,7 @@ vacuum_one_database(ConnParams *cparams,
}
ParallelSlotSetHandler(free_slot, TableCommandResultHandler, NULL);
- run_vacuum_command(free_slot->connection, cmd, echo, NULL);
+ run_vacuum_command(free_slot->connection, vacopts, cmd, echo, NULL);
if (!ParallelSlotsWaitCompletion(sa))
ret = EXIT_FAILURE; /* error already reported by handler */
@@ -636,6 +653,35 @@ retrieve_objects(PGconn *conn, vacuumingOptions *vacopts,
" AND listed_objects.object_oid IS NOT NULL\n");
}
+ /*
+ * In REPACK mode, if the 'using_index' option was given but no index
+ * name, filter only tables that have an index with indisclustered set.
+ * (If an index name is given, we trust the user to pass a reasonable list
+ * of tables.)
+ *
+ * XXX it may be worth printing an error if an index name is given with no
+ * list of tables.
+ */
+ if (vacopts->mode == MODE_REPACK &&
+ vacopts->using_index && !vacopts->indexname)
+ {
+ appendPQExpBufferStr(&catalog_query,
+ " AND EXISTS (SELECT 1 FROM pg_catalog.pg_index\n"
+ " WHERE indrelid = c.oid AND indisclustered)\n");
+ }
+
+ /*
+ * In REPACK mode, only consider the tables that the current user has
+ * MAINTAIN privileges on. XXX maybe we should do this in all cases, not
+ * just REPACK. The vacuumdb output is too noisy for no reason.
+ */
+ if (vacopts->mode == MODE_REPACK)
+ {
+ appendPQExpBufferStr(&catalog_query,
+ " AND pg_catalog.has_table_privilege(current_user, "
+ "c.oid, 'MAINTAIN')\n");
+ }
+
/*
* If no tables were listed, filter for the relevant relation types. If
* tables were given via --table, don't bother filtering by relation type.
@@ -874,8 +920,10 @@ prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
if (vacopts->verbose)
appendPQExpBufferStr(sql, " VERBOSE");
}
+
+ appendPQExpBuffer(sql, " %s", table);
}
- else
+ else if (vacopts->mode == MODE_VACUUM)
{
appendPQExpBufferStr(sql, "VACUUM");
@@ -989,9 +1037,39 @@ prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
if (vacopts->and_analyze)
appendPQExpBufferStr(sql, " ANALYZE");
}
+
+ appendPQExpBuffer(sql, " %s", table);
+ }
+ else if (vacopts->mode == MODE_REPACK)
+ {
+ appendPQExpBufferStr(sql, "REPACK");
+
+ if (vacopts->verbose)
+ {
+ appendPQExpBuffer(sql, "%sVERBOSE", sep);
+ sep = comma;
+ }
+ if (vacopts->and_analyze)
+ {
+ appendPQExpBuffer(sql, "%sANALYZE", sep);
+ sep = comma;
+ }
+
+ if (sep != paren)
+ appendPQExpBufferChar(sql, ')');
+
+ appendPQExpBuffer(sql, " %s", table);
+
+ if (vacopts->using_index)
+ {
+ appendPQExpBuffer(sql, " USING INDEX");
+ if (vacopts->indexname)
+ appendPQExpBuffer(sql, " %s", fmtIdEnc(vacopts->indexname,
+ PQclientEncoding(conn)));
+ }
}
- appendPQExpBuffer(sql, " %s;", table);
+ appendPQExpBufferChar(sql, ';');
}
/*
@@ -1001,8 +1079,8 @@ prepare_vacuum_command(PGconn *conn, PQExpBuffer sql,
* Any errors during command execution are reported to stderr.
*/
static void
-run_vacuum_command(PGconn *conn, const char *sql, bool echo,
- const char *table)
+run_vacuum_command(PGconn *conn, vacuumingOptions *vacopts,
+ const char *sql, bool echo, const char *table)
{
bool status;
@@ -1015,13 +1093,21 @@ run_vacuum_command(PGconn *conn, const char *sql, bool echo,
{
if (table)
{
- pg_log_error("vacuuming of table \"%s\" in database \"%s\" failed: %s",
- table, PQdb(conn), PQerrorMessage(conn));
+ if (vacopts->mode == MODE_VACUUM)
+ pg_log_error("vacuuming of table \"%s\" in database \"%s\" failed: %s",
+ table, PQdb(conn), PQerrorMessage(conn));
+ else
+ pg_log_error("repacking of table \"%s\" in database \"%s\" failed: %s",
+ table, PQdb(conn), PQerrorMessage(conn));
}
else
{
- pg_log_error("vacuuming of database \"%s\" failed: %s",
- PQdb(conn), PQerrorMessage(conn));
+ if (vacopts->mode == MODE_VACUUM)
+ pg_log_error("vacuuming of database \"%s\" failed: %s",
+ PQdb(conn), PQerrorMessage(conn));
+ else
+ pg_log_error("repacking of database \"%s\" failed: %s",
+ PQdb(conn), PQerrorMessage(conn));
}
}
}
diff --git a/src/bin/scripts/vacuuming.h b/src/bin/scripts/vacuuming.h
index 49f968b32e5..665dbaedfad 100644
--- a/src/bin/scripts/vacuuming.h
+++ b/src/bin/scripts/vacuuming.h
@@ -20,6 +20,7 @@
typedef enum
{
MODE_VACUUM,
+ MODE_REPACK,
MODE_ANALYZE,
MODE_ANALYZE_IN_STAGES
} RunMode;
@@ -37,6 +38,8 @@ typedef struct vacuumingOptions
bool and_analyze;
bool full;
bool freeze;
+ bool using_index;
+ char *indexname;
bool disable_page_skipping;
bool skip_locked;
int min_xid_age;
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index 60088a64cbb..652542e8e65 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -24,6 +24,7 @@
#define CLUOPT_RECHECK 0x02 /* recheck relation state */
#define CLUOPT_RECHECK_ISCLUSTERED 0x04 /* recheck relation state for
* indisclustered */
+#define CLUOPT_ANALYZE 0x08 /* do an ANALYZE */
/* options for CLUSTER */
typedef struct ClusterParams
@@ -31,8 +32,11 @@ typedef struct ClusterParams
bits32 options; /* bitmask of CLUOPT_* */
} ClusterParams;
-extern void cluster(ParseState *pstate, ClusterStmt *stmt, bool isTopLevel);
-extern void cluster_rel(Relation OldHeap, Oid indexOid, ClusterParams *params);
+
+extern void ExecRepack(ParseState *pstate, RepackStmt *stmt, bool isTopLevel);
+
+extern void cluster_rel(RepackCommand command, Relation OldHeap, Oid indexOid,
+ ClusterParams *params);
extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
LOCKMODE lockmode);
extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
diff --git a/src/include/commands/progress.h b/src/include/commands/progress.h
index 1cde4bd9bcf..ebf004b7aa5 100644
--- a/src/include/commands/progress.h
+++ b/src/include/commands/progress.h
@@ -56,28 +56,34 @@
#define PROGRESS_ANALYZE_PHASE_COMPUTE_EXT_STATS 4
#define PROGRESS_ANALYZE_PHASE_FINALIZE_ANALYZE 5
-/* Progress parameters for cluster */
-#define PROGRESS_CLUSTER_COMMAND 0
-#define PROGRESS_CLUSTER_PHASE 1
-#define PROGRESS_CLUSTER_INDEX_RELID 2
-#define PROGRESS_CLUSTER_HEAP_TUPLES_SCANNED 3
-#define PROGRESS_CLUSTER_HEAP_TUPLES_WRITTEN 4
-#define PROGRESS_CLUSTER_TOTAL_HEAP_BLKS 5
-#define PROGRESS_CLUSTER_HEAP_BLKS_SCANNED 6
-#define PROGRESS_CLUSTER_INDEX_REBUILD_COUNT 7
+/*
+ * Progress parameters for REPACK.
+ *
+ * Values for PROGRESS_REPACK_COMMAND are defined as in RepackCommand.
+ *
+ * Note: Since REPACK shares code with CLUSTER, these values are also
+ * used by CLUSTER. (CLUSTER is now deprecated, so it makes little sense to
+ * introduce a separate set of constants.)
+ */
+#define PROGRESS_REPACK_COMMAND 0
+#define PROGRESS_REPACK_PHASE 1
+#define PROGRESS_REPACK_INDEX_RELID 2
+#define PROGRESS_REPACK_HEAP_TUPLES_SCANNED 3
+#define PROGRESS_REPACK_HEAP_TUPLES_WRITTEN 4
+#define PROGRESS_REPACK_TOTAL_HEAP_BLKS 5
+#define PROGRESS_REPACK_HEAP_BLKS_SCANNED 6
+#define PROGRESS_REPACK_INDEX_REBUILD_COUNT 7
-/* Phases of cluster (as advertised via PROGRESS_CLUSTER_PHASE) */
-#define PROGRESS_CLUSTER_PHASE_SEQ_SCAN_HEAP 1
-#define PROGRESS_CLUSTER_PHASE_INDEX_SCAN_HEAP 2
-#define PROGRESS_CLUSTER_PHASE_SORT_TUPLES 3
-#define PROGRESS_CLUSTER_PHASE_WRITE_NEW_HEAP 4
-#define PROGRESS_CLUSTER_PHASE_SWAP_REL_FILES 5
-#define PROGRESS_CLUSTER_PHASE_REBUILD_INDEX 6
-#define PROGRESS_CLUSTER_PHASE_FINAL_CLEANUP 7
-
-/* Commands of PROGRESS_CLUSTER */
-#define PROGRESS_CLUSTER_COMMAND_CLUSTER 1
-#define PROGRESS_CLUSTER_COMMAND_VACUUM_FULL 2
+/*
+ * Phases of repack (as advertised via PROGRESS_REPACK_PHASE).
+ */
+#define PROGRESS_REPACK_PHASE_SEQ_SCAN_HEAP 1
+#define PROGRESS_REPACK_PHASE_INDEX_SCAN_HEAP 2
+#define PROGRESS_REPACK_PHASE_SORT_TUPLES 3
+#define PROGRESS_REPACK_PHASE_WRITE_NEW_HEAP 4
+#define PROGRESS_REPACK_PHASE_SWAP_REL_FILES 5
+#define PROGRESS_REPACK_PHASE_REBUILD_INDEX 6
+#define PROGRESS_REPACK_PHASE_FINAL_CLEANUP 7
/* Progress parameters for CREATE INDEX */
/* 3, 4 and 5 reserved for "waitfor" metrics */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ecbddd12e1b..525f6e6d6a5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -3951,18 +3951,6 @@ typedef struct AlterSystemStmt
VariableSetStmt *setstmt; /* SET subcommand */
} AlterSystemStmt;
-/* ----------------------
- * Cluster Statement (support pbrown's cluster index implementation)
- * ----------------------
- */
-typedef struct ClusterStmt
-{
- NodeTag type;
- RangeVar *relation; /* relation being indexed, or NULL if all */
- char *indexname; /* original index defined */
- List *params; /* list of DefElem nodes */
-} ClusterStmt;
-
/* ----------------------
* Vacuum and Analyze Statements
*
@@ -3975,7 +3963,7 @@ typedef struct VacuumStmt
NodeTag type;
List *options; /* list of DefElem nodes */
List *rels; /* list of VacuumRelation, or NIL for all */
- bool is_vacuumcmd; /* true for VACUUM, false for ANALYZE */
+ bool is_vacuumcmd; /* true for VACUUM, false otherwise */
} VacuumStmt;
/*
@@ -3993,6 +3981,27 @@ typedef struct VacuumRelation
List *va_cols; /* list of column names, or NIL for all */
} VacuumRelation;
+/* ----------------------
+ * Repack Statement
+ * ----------------------
+ */
+typedef enum RepackCommand
+{
+ REPACK_COMMAND_CLUSTER = 1,
+ REPACK_COMMAND_REPACK,
+ REPACK_COMMAND_VACUUMFULL,
+} RepackCommand;
+
+typedef struct RepackStmt
+{
+ NodeTag type;
+ RepackCommand command; /* type of command being run */
+ VacuumRelation *relation; /* relation being repacked */
+ char *indexname; /* order tuples by this index */
+ bool usingindex; /* whether USING INDEX is specified */
+ List *params; /* list of DefElem nodes */
+} RepackStmt;
+
/* ----------------------
* Explain Statement
*
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 84182eaaae2..87f6c226c43 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -375,6 +375,7 @@ PG_KEYWORD("reindex", REINDEX, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("relative", RELATIVE_P, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("release", RELEASE, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("rename", RENAME, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("repack", REPACK, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/tcop/cmdtaglist.h b/src/include/tcop/cmdtaglist.h
index d250a714d59..cceb312f2b3 100644
--- a/src/include/tcop/cmdtaglist.h
+++ b/src/include/tcop/cmdtaglist.h
@@ -196,6 +196,7 @@ PG_CMDTAG(CMDTAG_REASSIGN_OWNED, "REASSIGN OWNED", false, false, false)
PG_CMDTAG(CMDTAG_REFRESH_MATERIALIZED_VIEW, "REFRESH MATERIALIZED VIEW", true, false, false)
PG_CMDTAG(CMDTAG_REINDEX, "REINDEX", true, false, false)
PG_CMDTAG(CMDTAG_RELEASE, "RELEASE", false, false, false)
+PG_CMDTAG(CMDTAG_REPACK, "REPACK", false, false, false)
PG_CMDTAG(CMDTAG_RESET, "RESET", false, false, false)
PG_CMDTAG(CMDTAG_REVOKE, "REVOKE", true, false, false)
PG_CMDTAG(CMDTAG_REVOKE_ROLE, "REVOKE ROLE", false, false, false)
diff --git a/src/include/utils/backend_progress.h b/src/include/utils/backend_progress.h
index dda813ab407..e69e366dcdc 100644
--- a/src/include/utils/backend_progress.h
+++ b/src/include/utils/backend_progress.h
@@ -28,6 +28,7 @@ typedef enum ProgressCommandType
PROGRESS_COMMAND_CREATE_INDEX,
PROGRESS_COMMAND_BASEBACKUP,
PROGRESS_COMMAND_COPY,
+ PROGRESS_COMMAND_REPACK,
} ProgressCommandType;
#define PGSTAT_NUM_PROGRESS_PARAM 20
diff --git a/src/test/regress/expected/cluster.out b/src/test/regress/expected/cluster.out
index 4d40a6809ab..277854418fa 100644
--- a/src/test/regress/expected/cluster.out
+++ b/src/test/regress/expected/cluster.out
@@ -495,6 +495,43 @@ ALTER TABLE clstrpart SET WITHOUT CLUSTER;
ERROR: cannot mark index clustered in partitioned table
ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
ERROR: cannot mark index clustered in partitioned table
+-- Check that REPACK sets new relfilenodes: it should process exactly the same
+-- tables as CLUSTER did.
+DROP TABLE old_cluster_info;
+DROP TABLE new_cluster_info;
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+REPACK clstrpart USING INDEX clstrpart_idx;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+ relname | level | relkind | ?column?
+-------------+-------+---------+----------
+ clstrpart | 0 | p | t
+ clstrpart1 | 1 | p | t
+ clstrpart11 | 2 | r | f
+ clstrpart12 | 2 | p | t
+ clstrpart2 | 1 | r | f
+ clstrpart3 | 1 | p | t
+ clstrpart33 | 2 | r | f
+(7 rows)
+
+-- And finally the same for REPACK w/o index.
+DROP TABLE old_cluster_info;
+DROP TABLE new_cluster_info;
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+REPACK clstrpart;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+ relname | level | relkind | ?column?
+-------------+-------+---------+----------
+ clstrpart | 0 | p | t
+ clstrpart1 | 1 | p | t
+ clstrpart11 | 2 | r | f
+ clstrpart12 | 2 | p | t
+ clstrpart2 | 1 | r | f
+ clstrpart3 | 1 | p | t
+ clstrpart33 | 2 | r | f
+(7 rows)
+
DROP TABLE clstrpart;
-- Ownership of partitions is checked
CREATE TABLE ptnowner(i int unique) PARTITION BY LIST (i);
@@ -513,7 +550,7 @@ CREATE TEMP TABLE ptnowner_oldnodes AS
JOIN pg_class AS c ON c.oid=tree.relid;
SET SESSION AUTHORIZATION regress_ptnowner;
CLUSTER ptnowner USING ptnowner_i_idx;
-WARNING: permission denied to cluster "ptnowner2", skipping it
+WARNING: permission denied to execute CLUSTER on "ptnowner2", skipping it
RESET SESSION AUTHORIZATION;
SELECT a.relname, a.relfilenode=b.relfilenode FROM pg_class a
JOIN ptnowner_oldnodes b USING (oid) ORDER BY a.relname COLLATE "C";
@@ -665,6 +702,101 @@ SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
(4 rows)
COMMIT;
+----------------------------------------------------------------------
+--
+-- REPACK
+--
+----------------------------------------------------------------------
+-- REPACK handles individual tables identically to CLUSTER, but it's worth
+-- checking if it handles table hierarchies identically as well.
+REPACK clstr_tst USING INDEX clstr_tst_c;
+-- Verify that inheritance link still works
+INSERT INTO clstr_tst_inh VALUES (0, 100, 'in child table 2');
+SELECT a,b,c,substring(d for 30), length(d) from clstr_tst;
+ a | b | c | substring | length
+----+-----+------------------+--------------------------------+--------
+ 10 | 14 | catorce | |
+ 18 | 5 | cinco | |
+ 9 | 4 | cuatro | |
+ 26 | 19 | diecinueve | |
+ 12 | 18 | dieciocho | |
+ 30 | 16 | dieciseis | |
+ 24 | 17 | diecisiete | |
+ 2 | 10 | diez | |
+ 23 | 12 | doce | |
+ 11 | 2 | dos | |
+ 25 | 9 | nueve | |
+ 31 | 8 | ocho | |
+ 1 | 11 | once | |
+ 28 | 15 | quince | |
+ 32 | 6 | seis | xyzzyxyzzyxyzzyxyzzyxyzzyxyzzy | 500000
+ 29 | 7 | siete | |
+ 15 | 13 | trece | |
+ 22 | 30 | treinta | |
+ 17 | 32 | treinta y dos | |
+ 3 | 31 | treinta y uno | |
+ 5 | 3 | tres | |
+ 20 | 1 | uno | |
+ 6 | 20 | veinte | |
+ 14 | 25 | veinticinco | |
+ 21 | 24 | veinticuatro | |
+ 4 | 22 | veintidos | |
+ 19 | 29 | veintinueve | |
+ 16 | 28 | veintiocho | |
+ 27 | 26 | veintiseis | |
+ 13 | 27 | veintisiete | |
+ 7 | 23 | veintitres | |
+ 8 | 21 | veintiuno | |
+ 0 | 100 | in child table | |
+ 0 | 100 | in child table 2 | |
+(34 rows)
+
+-- Verify that foreign key link still works
+INSERT INTO clstr_tst (b, c) VALUES (1111, 'this should fail');
+ERROR: insert or update on table "clstr_tst" violates foreign key constraint "clstr_tst_con"
+DETAIL: Key (b)=(1111) is not present in table "clstr_tst_s".
+SELECT conname FROM pg_constraint WHERE conrelid = 'clstr_tst'::regclass
+ORDER BY 1;
+ conname
+----------------------
+ clstr_tst_a_not_null
+ clstr_tst_con
+ clstr_tst_pkey
+(3 rows)
+
+-- Verify partial analyze works
+REPACK (ANALYZE) clstr_tst (a);
+REPACK (ANALYZE) clstr_tst;
+REPACK (VERBOSE) clstr_tst (a);
+ERROR: ANALYZE option must be specified when a column list is provided
+-- REPACK w/o argument performs no ordering, so we can only check which tables
+-- have the relfilenode changed.
+RESET SESSION AUTHORIZATION;
+CREATE TEMP TABLE relnodes_old AS
+(SELECT relname, relfilenode
+FROM pg_class
+WHERE relname IN ('clstr_1', 'clstr_2', 'clstr_3'));
+SET SESSION AUTHORIZATION regress_clstr_user;
+SET client_min_messages = ERROR; -- order of "skipping" warnings may vary
+REPACK;
+RESET client_min_messages;
+RESET SESSION AUTHORIZATION;
+CREATE TEMP TABLE relnodes_new AS
+(SELECT relname, relfilenode
+FROM pg_class
+WHERE relname IN ('clstr_1', 'clstr_2', 'clstr_3'));
+-- Do the actual comparison. Unlike CLUSTER, clstr_3 should have been
+-- processed because there is nothing like clustering index here.
+SELECT o.relname FROM relnodes_old o
+JOIN relnodes_new n ON o.relname = n.relname
+WHERE o.relfilenode <> n.relfilenode
+ORDER BY o.relname;
+ relname
+---------
+ clstr_1
+ clstr_3
+(2 rows)
+
-- clean up
DROP TABLE clustertest;
DROP TABLE clstr_1;
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 77e25ca029e..bd872ebd13a 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1994,34 +1994,23 @@ pg_stat_progress_basebackup| SELECT pid,
ELSE NULL::text
END AS backup_type
FROM pg_stat_get_progress_info('BASEBACKUP'::text) s(pid, datid, relid, param1, param2, param3, param4, param5, param6, param7, param8, param9, param10, param11, param12, param13, param14, param15, param16, param17, param18, param19, param20);
-pg_stat_progress_cluster| SELECT s.pid,
- s.datid,
- d.datname,
- s.relid,
- CASE s.param1
- WHEN 1 THEN 'CLUSTER'::text
- WHEN 2 THEN 'VACUUM FULL'::text
- ELSE NULL::text
+pg_stat_progress_cluster| SELECT pid,
+ datid,
+ datname,
+ relid,
+ CASE
+ WHEN (command = ANY (ARRAY['CLUSTER'::text, 'VACUUM FULL'::text])) THEN command
+ WHEN (repack_index_relid = (0)::oid) THEN 'VACUUM FULL'::text
+ ELSE 'CLUSTER'::text
END AS command,
- CASE s.param2
- WHEN 0 THEN 'initializing'::text
- WHEN 1 THEN 'seq scanning heap'::text
- WHEN 2 THEN 'index scanning heap'::text
- WHEN 3 THEN 'sorting tuples'::text
- WHEN 4 THEN 'writing new heap'::text
- WHEN 5 THEN 'swapping relation files'::text
- WHEN 6 THEN 'rebuilding index'::text
- WHEN 7 THEN 'performing final cleanup'::text
- ELSE NULL::text
- END AS phase,
- (s.param3)::oid AS cluster_index_relid,
- s.param4 AS heap_tuples_scanned,
- s.param5 AS heap_tuples_written,
- s.param6 AS heap_blks_total,
- s.param7 AS heap_blks_scanned,
- s.param8 AS index_rebuild_count
- FROM (pg_stat_get_progress_info('CLUSTER'::text) s(pid, datid, relid, param1, param2, param3, param4, param5, param6, param7, param8, param9, param10, param11, param12, param13, param14, param15, param16, param17, param18, param19, param20)
- LEFT JOIN pg_database d ON ((s.datid = d.oid)));
+ phase,
+ repack_index_relid AS cluster_index_relid,
+ heap_tuples_scanned,
+ heap_tuples_written,
+ heap_blks_total,
+ heap_blks_scanned,
+ index_rebuild_count
+ FROM pg_stat_progress_repack;
pg_stat_progress_copy| SELECT s.pid,
s.datid,
d.datname,
@@ -2081,6 +2070,35 @@ pg_stat_progress_create_index| SELECT s.pid,
s.param15 AS partitions_done
FROM (pg_stat_get_progress_info('CREATE INDEX'::text) s(pid, datid, relid, param1, param2, param3, param4, param5, param6, param7, param8, param9, param10, param11, param12, param13, param14, param15, param16, param17, param18, param19, param20)
LEFT JOIN pg_database d ON ((s.datid = d.oid)));
+pg_stat_progress_repack| SELECT s.pid,
+ s.datid,
+ d.datname,
+ s.relid,
+ CASE s.param1
+ WHEN 1 THEN 'CLUSTER'::text
+ WHEN 2 THEN 'REPACK'::text
+ WHEN 3 THEN 'VACUUM FULL'::text
+ ELSE NULL::text
+ END AS command,
+ CASE s.param2
+ WHEN 0 THEN 'initializing'::text
+ WHEN 1 THEN 'seq scanning heap'::text
+ WHEN 2 THEN 'index scanning heap'::text
+ WHEN 3 THEN 'sorting tuples'::text
+ WHEN 4 THEN 'writing new heap'::text
+ WHEN 5 THEN 'swapping relation files'::text
+ WHEN 6 THEN 'rebuilding index'::text
+ WHEN 7 THEN 'performing final cleanup'::text
+ ELSE NULL::text
+ END AS phase,
+ (s.param3)::oid AS repack_index_relid,
+ s.param4 AS heap_tuples_scanned,
+ s.param5 AS heap_tuples_written,
+ s.param6 AS heap_blks_total,
+ s.param7 AS heap_blks_scanned,
+ s.param8 AS index_rebuild_count
+ FROM (pg_stat_get_progress_info('REPACK'::text) s(pid, datid, relid, param1, param2, param3, param4, param5, param6, param7, param8, param9, param10, param11, param12, param13, param14, param15, param16, param17, param18, param19, param20)
+ LEFT JOIN pg_database d ON ((s.datid = d.oid)));
pg_stat_progress_vacuum| SELECT s.pid,
s.datid,
d.datname,
diff --git a/src/test/regress/sql/cluster.sql b/src/test/regress/sql/cluster.sql
index b7115f86104..c976823a3cb 100644
--- a/src/test/regress/sql/cluster.sql
+++ b/src/test/regress/sql/cluster.sql
@@ -76,7 +76,6 @@ INSERT INTO clstr_tst (b, c) VALUES (1111, 'this should fail');
SELECT conname FROM pg_constraint WHERE conrelid = 'clstr_tst'::regclass
ORDER BY 1;
-
SELECT relname, relkind,
EXISTS(SELECT 1 FROM pg_class WHERE oid = c.reltoastrelid) AS hastoast
FROM pg_class c WHERE relname LIKE 'clstr_tst%' ORDER BY relname;
@@ -229,6 +228,24 @@ SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM o
CLUSTER clstrpart;
ALTER TABLE clstrpart SET WITHOUT CLUSTER;
ALTER TABLE clstrpart CLUSTER ON clstrpart_idx;
+
+-- Check that REPACK sets new relfilenodes: it should process exactly the same
+-- tables as CLUSTER did.
+DROP TABLE old_cluster_info;
+DROP TABLE new_cluster_info;
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+REPACK clstrpart USING INDEX clstrpart_idx;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+
+-- And finally the same for REPACK w/o index.
+DROP TABLE old_cluster_info;
+DROP TABLE new_cluster_info;
+CREATE TEMP TABLE old_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+REPACK clstrpart;
+CREATE TEMP TABLE new_cluster_info AS SELECT relname, level, relfilenode, relkind FROM pg_partition_tree('clstrpart'::regclass) AS tree JOIN pg_class c ON c.oid=tree.relid ;
+SELECT relname, old.level, old.relkind, old.relfilenode = new.relfilenode FROM old_cluster_info AS old JOIN new_cluster_info AS new USING (relname) ORDER BY relname COLLATE "C";
+
DROP TABLE clstrpart;
-- Ownership of partitions is checked
@@ -313,6 +330,57 @@ EXPLAIN (COSTS OFF) SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
SELECT * FROM clstr_expression WHERE -a = -3 ORDER BY -a, b;
COMMIT;
+----------------------------------------------------------------------
+--
+-- REPACK
+--
+----------------------------------------------------------------------
+
+-- REPACK handles individual tables identically to CLUSTER, but it's worth
+-- checking if it handles table hierarchies identically as well.
+REPACK clstr_tst USING INDEX clstr_tst_c;
+
+-- Verify that inheritance link still works
+INSERT INTO clstr_tst_inh VALUES (0, 100, 'in child table 2');
+SELECT a,b,c,substring(d for 30), length(d) from clstr_tst;
+
+-- Verify that foreign key link still works
+INSERT INTO clstr_tst (b, c) VALUES (1111, 'this should fail');
+
+SELECT conname FROM pg_constraint WHERE conrelid = 'clstr_tst'::regclass
+ORDER BY 1;
+
+-- Verify partial analyze works
+REPACK (ANALYZE) clstr_tst (a);
+REPACK (ANALYZE) clstr_tst;
+REPACK (VERBOSE) clstr_tst (a);
+
+-- REPACK w/o argument performs no ordering, so we can only check which tables
+-- have the relfilenode changed.
+RESET SESSION AUTHORIZATION;
+CREATE TEMP TABLE relnodes_old AS
+(SELECT relname, relfilenode
+FROM pg_class
+WHERE relname IN ('clstr_1', 'clstr_2', 'clstr_3'));
+
+SET SESSION AUTHORIZATION regress_clstr_user;
+SET client_min_messages = ERROR; -- order of "skipping" warnings may vary
+REPACK;
+RESET client_min_messages;
+
+RESET SESSION AUTHORIZATION;
+CREATE TEMP TABLE relnodes_new AS
+(SELECT relname, relfilenode
+FROM pg_class
+WHERE relname IN ('clstr_1', 'clstr_2', 'clstr_3'));
+
+-- Do the actual comparison. Unlike CLUSTER, clstr_3 should have been
+-- processed because there is nothing like clustering index here.
+SELECT o.relname FROM relnodes_old o
+JOIN relnodes_new n ON o.relname = n.relname
+WHERE o.relfilenode <> n.relfilenode
+ORDER BY o.relname;
+
-- clean up
DROP TABLE clustertest;
DROP TABLE clstr_1;
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 018b5919cf6..0c7dd5d09e8 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2544,6 +2544,8 @@ ReorderBufferTupleCidKey
ReorderBufferUpdateProgressTxnCB
ReorderTuple
RepOriginId
+RepackCommand
+RepackStmt
ReparameterizeForeignPathByChild_function
ReplaceVarsFromTargetList_context
ReplaceVarsNoMatchOption
--
2.47.3
--ecl2euvoqutt27wj
Content-Type: text/x-diff; charset=utf-8
Content-Disposition: attachment;
filename="v25-0002-Refactor-index_concurrently_create_copy-for-use-.patch"
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* [PATCH v1] Add per-backend AIO statistics
@ 2026-06-11 09:45 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-06-11 09:45 UTC (permalink / raw)
This commit adds per-backend AIO statistics, providing per-backend AIO behavior
details.
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns the following counters based on the PID
provided in input:
- started: total number of AIO operations initiated
- executed_sync: IOs that were executed synchronously (fallback path)
- executed_async: IOs that were submitted asynchronously to the IO method
- completed_self: IO completions processed by the issuing backend itself
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times the backend had to wait for a free AIO handle
- submitted: number of submitted calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion
patterns. That helps see how IO completion work is distributed and could
help interpret per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
This commit is straight-forward, relying on the infrastructure provided
by 9aea73fc61d4 (backend-level pgstats).
XXX: Bump catalog version. No need to touch PGSTAT_FILE_FORMAT_ID as backend
statistics are never written to disk.
Author: Bertrand Drouvot <[email protected]>
Reviewed-by:
Discussion:
---
doc/src/sgml/monitoring.sgml | 70 +++++++++++++
src/backend/storage/aio/aio.c | 13 +++
src/backend/utils/activity/pgstat_backend.c | 109 ++++++++++++++++++++
src/backend/utils/adt/pgstatfuncs.c | 60 +++++++++++
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 25 +++++
src/include/utils/pgstat_internal.h | 3 +-
src/test/modules/test_aio/t/001_aio.pl | 32 ++++++
src/tools/pgindent/typedefs.list | 1 +
9 files changed, 319 insertions(+), 1 deletion(-)
24.4% doc/src/sgml/
3.2% src/backend/storage/aio/
25.3% src/backend/utils/activity/
20.5% src/backend/utils/adt/
4.9% src/include/catalog/
10.0% src/include/
11.1% src/test/modules/test_aio/t/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 12b9ee20d4a..1c566cf0e0e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5641,6 +5641,76 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-aio" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_aio</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_aio</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns <acronym>AIO</acronym> (Asynchronous I/O) statistics about the
+ backend with the specified process ID. The returned values are:
+ <itemizedlist>
+ <listitem>
+ <para>
+ <literal>started</literal>: Total IOs initiated.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_sync</literal>: IOs executed synchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>executed_async</literal>: IOs submitted asynchronously.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_self</literal>: IO completions processed by this
+ backend.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>completed_other</literal>: IO completions processed on
+ behalf of other backends.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>handle_waits</literal>: Times waited for a free AIO handle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>submitted</literal>: Number of submit calls to the IO
+ method. Compare with <literal>executed_async</literal> to determine
+ average batch size.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>stats_reset</literal>: Timestamp of last stats reset.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The <literal>completed_other</literal> column is only meaningful
+ when <varname>io_method</varname> is set to <literal>io_uring</literal>;
+ with <literal>worker</literal> mode, IO completions are processed by
+ IO worker processes which do not track these statistics.
+ </para>
+ <para>
+ The function does not return AIO statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/storage/aio/aio.c b/src/backend/storage/aio/aio.c
index 8f7e26607b9..507f1727d41 100644
--- a/src/backend/storage/aio/aio.c
+++ b/src/backend/storage/aio/aio.c
@@ -40,6 +40,7 @@
#include "lib/ilist.h"
#include "miscadmin.h"
+#include "pgstat.h"
#include "port/atomics.h"
#include "storage/aio.h"
#include "storage/aio_internal.h"
@@ -458,6 +459,8 @@ pgaio_io_stage(PgAioHandle *ioh, PgAioOp op)
"staged (synchronous: %d, in_batch: %d)",
needs_synchronous, pgaio_my_backend->in_batchmode);
+ pgstat_count_backend_aio_start(needs_synchronous);
+
if (!needs_synchronous)
{
pgaio_my_backend->staged_ios[pgaio_my_backend->num_staged_ios++] = ioh;
@@ -544,6 +547,12 @@ pgaio_io_process_completion(PgAioHandle *ioh, int result)
/* condition variable broadcast ensures state is visible before wakeup */
ConditionVariableBroadcast(&ioh->cv);
+ /* Track AIO completion stats */
+ if (ioh->owner_procno == MyProcNumber)
+ pgstat_count_backend_aio_complete_self();
+ else
+ pgstat_count_backend_aio_complete_other();
+
/* contains call to pgaio_io_call_complete_local() */
if (ioh->owner_procno == MyProcNumber)
pgaio_io_reclaim(ioh);
@@ -762,6 +771,8 @@ pgaio_io_wait_for_free(void)
{
int reclaimed = 0;
+ pgstat_count_backend_aio_handle_wait();
+
pgaio_debug(DEBUG2, "waiting for free IO with %d pending, %u in-flight, %u idle IOs",
pgaio_my_backend->num_staged_ios,
dclist_count(&pgaio_my_backend->in_flight_ios),
@@ -1150,6 +1161,8 @@ pgaio_submit_staged(void)
Assert(total_submitted == did_submit);
+ pgstat_count_backend_aio_submitted();
+
pgaio_my_backend->num_staged_ios = 0;
pgaio_debug(DEBUG4,
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index b736b2ccc6f..4ad755f7f18 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -40,6 +40,7 @@
static PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
static bool backend_has_lockstats = false;
+static bool backend_has_aiostats = false;
/*
* WAL usage counters saved from pgWalUsage at the previous call to
@@ -120,6 +121,74 @@ pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type)
pgstat_report_fixed = true;
}
+/*
+ * Utility routines to report AIO stats for backends, kept here to avoid
+ * exposing PendingBackendStats to the outside world.
+ */
+void
+pgstat_count_backend_aio_start(bool synchronous)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.started++;
+ if (synchronous)
+ PendingBackendStats.aio_counters.executed_sync++;
+ else
+ PendingBackendStats.aio_counters.executed_async++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_self(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_self++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_complete_other(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.completed_other++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_handle_wait(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.handle_waits++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
+void
+pgstat_count_backend_aio_submitted(void)
+{
+ if (!pgstat_tracks_backend_bktype(MyBackendType))
+ return;
+
+ PendingBackendStats.aio_counters.submitted++;
+
+ backend_has_aiostats = true;
+ pgstat_report_fixed = true;
+}
+
/*
* Returns statistics of a backend by proc number.
*/
@@ -326,6 +395,38 @@ pgstat_flush_backend_entry_lock(PgStat_EntryRef *entry_ref)
backend_has_lockstats = false;
}
+/*
+ * Flush out locally pending backend AIO statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_aio(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_AioCounters *bktype_shstats;
+
+ if (!backend_has_aiostats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.aio_counters;
+
+#define AIOSTAT_ACC(fld) \
+ (bktype_shstats->fld += PendingBackendStats.aio_counters.fld)
+ AIOSTAT_ACC(started);
+ AIOSTAT_ACC(executed_sync);
+ AIOSTAT_ACC(executed_async);
+ AIOSTAT_ACC(completed_self);
+ AIOSTAT_ACC(completed_other);
+ AIOSTAT_ACC(handle_waits);
+ AIOSTAT_ACC(submitted);
+#undef AIOSTAT_ACC
+
+ MemSet(&PendingBackendStats.aio_counters, 0, sizeof(PgStat_AioCounters));
+
+ backend_has_aiostats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -354,6 +455,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if ((flags & PGSTAT_BACKEND_FLUSH_LOCK) && backend_has_lockstats)
has_pending_data = true;
+ /* Some AIO data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_AIO) && backend_has_aiostats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -372,6 +477,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_LOCK)
pgstat_flush_backend_entry_lock(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_AIO)
+ pgstat_flush_backend_entry_aio(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -411,6 +519,7 @@ pgstat_create_backend(ProcNumber procnum)
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
backend_has_iostats = false;
backend_has_lockstats = false;
+ backend_has_aiostats = false;
/*
* Initialize prevBackendWalUsage with pgWalUsage so that
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 565d0e70768..fb62a56f3fe 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1722,6 +1722,66 @@ pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
}
+/*
+ * Returns AIO statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_aio(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_BACKEND_AIO_COLS 8
+ TupleDesc tupdesc;
+ Datum values[PG_STAT_BACKEND_AIO_COLS] = {0};
+ bool nulls[PG_STAT_BACKEND_AIO_COLS] = {0};
+ int pid;
+ PgStat_Backend *backend_stats;
+ PgStat_AioCounters aio_counters;
+
+ pid = PG_GETARG_INT32(0);
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);
+
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ aio_counters = backend_stats->aio_counters;
+
+ /* Initialise attributes information in the tuple descriptor */
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_BACKEND_AIO_COLS);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "started",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "executed_sync",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 3, "executed_async",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 4, "completed_self",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 5, "completed_other",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 6, "handle_waits",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 7, "submitted",
+ INT8OID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 8, "stats_reset",
+ TIMESTAMPTZOID, -1, 0);
+ TupleDescFinalize(tupdesc);
+ BlessTupleDesc(tupdesc);
+
+ /* Fill values */
+ values[0] = Int64GetDatum(aio_counters.started);
+ values[1] = Int64GetDatum(aio_counters.executed_sync);
+ values[2] = Int64GetDatum(aio_counters.executed_async);
+ values[3] = Int64GetDatum(aio_counters.completed_self);
+ values[4] = Int64GetDatum(aio_counters.completed_other);
+ values[5] = Int64GetDatum(aio_counters.handle_waits);
+ values[6] = Int64GetDatum(aio_counters.submitted);
+
+ if (backend_stats->stat_reset_timestamp != 0)
+ values[7] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+ else
+ nulls[7] = true;
+
+ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
+}
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3cb84359adf..a089860ada4 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6108,6 +6108,13 @@
proargmodes => '{i,o,o,o,o,o}',
proargnames => '{backend_pid,locktype,waits,wait_time,fastpath_exceeded,stats_reset}',
prosrc => 'pg_stat_get_backend_lock' },
+{ oid => '9082', descr => 'statistics: backend AIO activity',
+ proname => 'pg_stat_get_backend_aio', provolatile => 'v', proparallel => 'r',
+ prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,started,executed_sync,executed_async,completed_self,completed_other,handle_waits,submitted,stats_reset}',
+ prosrc => 'pg_stat_get_backend_aio' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 58a44857f13..64afb2bc082 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -514,6 +514,21 @@ typedef struct PgStat_WalStats
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
+/* -------
+ * PgStat_AioCounters AIO activity counters
+ * -------
+ */
+typedef struct PgStat_AioCounters
+{
+ PgStat_Counter started;
+ PgStat_Counter executed_sync;
+ PgStat_Counter executed_async;
+ PgStat_Counter completed_self;
+ PgStat_Counter completed_other;
+ PgStat_Counter handle_waits;
+ PgStat_Counter submitted;
+} PgStat_AioCounters;
+
/* -------
* PgStat_Backend Backend statistics
* -------
@@ -524,6 +539,7 @@ typedef struct PgStat_Backend
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
PgStat_PendingLock lock_stats;
+ PgStat_AioCounters aio_counters;
} PgStat_Backend;
/* ---------
@@ -542,6 +558,8 @@ typedef struct PgStat_BackendPending
* PGSTAT_KIND_LOCK.
*/
PgStat_PendingLock pending_lock;
+ /* Store the AIO statistics counters */
+ PgStat_AioCounters aio_counters;
} PgStat_BackendPending;
/*
@@ -598,6 +616,13 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
extern void pgstat_count_backend_lock_waits(uint8 locktag_type, PgStat_Counter usecs);
extern void pgstat_count_backend_lock_fastpath_exceeded(uint8 locktag_type);
+/* used by aio.c for AIO stats tracked in backends */
+extern void pgstat_count_backend_aio_start(bool synchronous);
+extern void pgstat_count_backend_aio_complete_self(void);
+extern void pgstat_count_backend_aio_complete_other(void);
+extern void pgstat_count_backend_aio_handle_wait(void);
+extern void pgstat_count_backend_aio_submitted(void);
+
extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
BackendType *bktype);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index b3dc3ff7d8b..b2092fb42b9 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -706,7 +706,8 @@ extern void pgstat_archiver_snapshot_cb(void);
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
#define PGSTAT_BACKEND_FLUSH_LOCK (1 << 2) /* Flush lock statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK)
+#define PGSTAT_BACKEND_FLUSH_AIO (1 << 3) /* Flush AIO statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_LOCK | PGSTAT_BACKEND_FLUSH_AIO)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/modules/test_aio/t/001_aio.pl b/src/test/modules/test_aio/t/001_aio.pl
index 63cadd64c15..8ecf3d3ad91 100644
--- a/src/test/modules/test_aio/t/001_aio.pl
+++ b/src/test/modules/test_aio/t/001_aio.pl
@@ -1842,6 +1842,37 @@ read_buffers('$table', 0, 4)|,
$psql_c->quit();
}
+# Test per-backend AIO statistics counters
+sub test_aio_stats
+{
+ my $io_method = shift;
+ my $node = shift;
+
+ my $psql = $node->background_psql('postgres', on_error_stop => 0);
+
+ # Reset backend stats, evict relation, then read it back to force
+ # physical IO through the AIO layer.
+ $psql->query_safe(qq(SELECT pg_stat_reset_backend_stats(pg_backend_pid())));
+ $psql->query_safe(qq(SELECT evict_rel('tbl_ok')));
+ $psql->query_safe(qq(SELECT count(*) FROM tbl_ok));
+ $psql->query_safe(qq(SELECT pg_stat_force_next_flush()));
+
+ # started must be > 0 after physical IO
+ my $started = $psql->query_safe(
+ qq(SELECT started FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ cmp_ok($started, '>', 0,
+ "$io_method: AIO stats: started > 0 after physical IO");
+
+ # invariant: started = executed_sync + executed_async
+ my $consistent = $psql->query_safe(
+ qq(SELECT started = executed_sync + executed_async
+ FROM pg_stat_get_backend_aio(pg_backend_pid())));
+ is($consistent, 't',
+ "$io_method: AIO stats: started = executed_sync + executed_async");
+
+ $psql->quit();
+}
+
# Run all tests that for the specified node / io_method
sub test_io_method
{
@@ -1878,6 +1909,7 @@ CHECKPOINT;
test_ignore_checksum($io_method, $node);
test_checksum_createdb($io_method, $node);
test_read_buffers($io_method, $node);
+ test_aio_stats($io_method, $node);
# generic injection tests
SKIP:
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 117e7379f10..6ce3077fa5b 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2329,6 +2329,7 @@ PgStatShared_ReplSlot
PgStatShared_SLRU
PgStatShared_Subscription
PgStatShared_Wal
+PgStat_AioCounters
PgStat_ArchiverStats
PgStat_Backend
PgStat_BackendPending
--
2.34.1
--Pi0/Nu3LVhi0Ij+H--
^ permalink raw reply [nested|flat] 44+ messages in thread
* Add per-backend AIO statistics
@ 2026-07-07 11:02 Bertrand Drouvot <[email protected]>
0 siblings, 2 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-07-07 11:02 UTC (permalink / raw)
To: [email protected]
Hi hackers,
Currently to monitor AIO we can use:
1/ pg_aios that lists all AIO handles that are currently in use. That shows
what's happening right now, but not what has happened.
2/ pg_stat_get_backend_io() that shows how much IO was done, but not how it
was done. There's no way to see whether IOs ran synchronously or
asynchronously, whether a backend was stalling on handle exhaustion, or how
completions are distributed across backends.
This patch helps answering those questions by exposing cumulative per-backend
AIO counters:
- started: total AIO operations initiated
- executed_sync: IOs executed synchronously (fallback path)
- executed_async: IOs submitted asynchronously
- completed_self: IO completions processed by the issuing backend
- completed_other: IO completions processed on behalf of another backend
- handle_waits: times waited for a free AIO handle
- submitted: number of submit calls to the IO method
These counters are useful for understanding and tuning AIO behavior:
- executed_async / started. A ratio near zero means the backend is falling back
to synchronous execution (TOAST chunk fetches, temp buffers, ...).
- a non-zero handle_waits means the backend exhausted all its AIO handles. That
could mean that io_max_concurrency is too low.
- completed_self vs completed_other reveals cross-backend completion patterns.
That helps see how IO completion work is distributed and could help interpret
per backend IO statistics values.
- executed_async / submitted gives the average batch size per submit call.
As far as the technical implementation:
This data can be retrieved with a new system function called
pg_stat_get_backend_aio(), that returns one row based on the PID provided in input.
pgstat_flush_backend() gains a new flag value, able to control the flush of the
AIO stats.
This patch relies mostly on the infrastructure provided by 9aea73fc61d4, that
has introduced backend statistics.
The overhead (4 functions calls and counters increments) kind of follow the same
patterns as pgstat_count_backend_io_op() and I did not observe measurable
regression (I did not expect to). Also that does not add that much memory
per-backend: PgStat_AioCounters is 56 bytes.
There is no "double" counting as a global view to show those counters does not
exist. I think that's better to start with the per-backend side of it and see
if we want to also add a global view. For example, completed_other identifies
which backends did IOs for other backends. Also this allows correlating with
pg_stat_activity and pg_stat_get_backend_io().
Examples based on Franck's blog post [1]:
1/ query the smalldocs table:
postgres=# select count(*),avg(length(data)) from smalldocs;
count | avg
---------+-----------------------
1024000 | 1024.0000000000000000
(1 row)
postgres=# SELECT * FROM pg_stat_get_backend_aio(pg_backend_pid());
started | executed_sync | executed_async | completed_self | completed_other | handle_waits | submitted | stats_reset
---------+---------------+----------------+----------------+-----------------+--------------+-----------+-------------------------------
3125 | 46 | 3079 | 46 | 0 | 0 | 3078 | 2026-07-07 09:28:27.412136+00
We can see that the sequential scan fully benefits from AIO.
2/ query the largedocs table:
postgres=# select count(*),avg(length(data)) from largedocs;
count | avg
-------+----------------------
1000 | 1048576.000000000000
(1 row)
postgres=# SELECT * FROM pg_stat_get_backend_aio(pg_backend_pid());
started | executed_sync | executed_async | completed_self | completed_other | handle_waits | submitted | stats_reset
---------+---------------+----------------+----------------+-----------------+--------------+-----------+-------------------------------
121154 | 121150 | 4 | 121150 | 0 | 0 | 4 | 2026-07-07 09:35:00.504872+00
We can see that the sequential scan bypasses AIO.
Looking forward to your feedback.
[1]: https://dev.to/franckpachot/iouring-buffered-reads-in-postgresql-19-iouring-mcn
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-08 06:00 Bertrand Drouvot <[email protected]>
parent: Bertrand Drouvot <[email protected]>
1 sibling, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-07-08 06:00 UTC (permalink / raw)
To: [email protected]
Hi,
On Tue, Jul 07, 2026 at 11:02:03AM +0000, Bertrand Drouvot wrote:
> postgres=# select count(*),avg(length(data)) from smalldocs;
> count | avg
> ---------+-----------------------
> 1024000 | 1024.0000000000000000
> (1 row)
>
> postgres=# SELECT * FROM pg_stat_get_backend_aio(pg_backend_pid());
> started | executed_sync | executed_async | completed_self | completed_other | handle_waits | submitted | stats_reset
> ---------+---------------+----------------+----------------+-----------------+--------------+-----------+-------------------------------
> 3125 | 46 | 3079 | 46 | 0 | 0 | 3078 | 2026-07-07 09:28:27.412136+00
>
> We can see that the sequential scan fully benefits from AIO.
>
> 2/ query the largedocs table:
>
> postgres=# select count(*),avg(length(data)) from largedocs;
> count | avg
> -------+----------------------
> 1000 | 1048576.000000000000
> (1 row)
>
> postgres=# SELECT * FROM pg_stat_get_backend_aio(pg_backend_pid());
> started | executed_sync | executed_async | completed_self | completed_other | handle_waits | submitted | stats_reset
> ---------+---------------+----------------+----------------+-----------------+--------------+-----------+-------------------------------
> 121154 | 121150 | 4 | 121150 | 0 | 0 | 4 | 2026-07-07 09:35:00.504872+00
>
> We can see that the sequential scan bypasses AIO.
I was just doing some AIO experiments and was using the new pg_stat_get_backend_aio()
function.
So, while at it, sharing more examples here:
3/ pg_stat_get_backend_aio() and pg_stat_get_backend_io() correlation
postgres=# SELECT executed_sync, executed_async FROM pg_stat_get_backend_aio(pg_backend_pid());
executed_sync | executed_async
---------------+----------------
46 | 3088
(1 row)
postgres=# SELECT object, context, reads, read_bytes FROM pg_stat_get_backend_io(pg_backend_pid());
object | context | reads | read_bytes
---------------+-----------+-------+------------
relation | bulkread | 3088 | 401580032
relation | bulkwrite | 0 | 0
relation | init | 0 | 0
relation | normal | 46 | 376832
relation | vacuum | 0 | 0
temp relation | normal | 0 | 0
wal | init | |
wal | normal | 0 | 0
(8 rows)
We can see that the "executed_sync" matches the reads "normal" context and that
the "executed_async" matches the reads "bulkread" context.
4/ io_uring and multiple backends
postgres=# SELECT a.pid,
(pg_stat_get_backend_aio(a.pid)).completed_other
FROM pg_stat_activity a
WHERE a.backend_type = 'client backend';
pid | completed_other
---------+-----------------
1911889 | 245
1911892 | 511
1911912 | 147
1911933 | 161
(4 rows)
We can see that the backends completed AIO on behalf of other backends, which
makes fully sense in io_uring mode.
5/ io_max_concurrency = 4
postgres=# SELECT started, handle_waits FROM pg_stat_get_backend_aio(pg_backend_pid());
started | handle_waits
---------+--------------
3139 | 3026
(1 row)
We can see that the backend had to wait for free AIO handles on 96% of its IOs.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-08 06:52 Michael Paquier <[email protected]>
parent: Bertrand Drouvot <[email protected]>
1 sibling, 2 replies; 44+ messages in thread
From: Michael Paquier @ 2026-07-08 06:52 UTC (permalink / raw)
To: Bertrand Drouvot <[email protected]>; +Cc: [email protected]; Andres Freund <[email protected]>
On Tue, Jul 07, 2026 at 11:02:03AM +0000, Bertrand Drouvot wrote:
> 1/ pg_aios that lists all AIO handles that are currently in use. That shows
> what's happening right now, but not what has happened.
>
> 2/ pg_stat_get_backend_io() that shows how much IO was done, but not how it
> was done. There's no way to see whether IOs ran synchronously or
> asynchronously, whether a backend was stalling on handle exhaustion, or how
> completions are distributed across backends.
While the information may be useful, one thing that sounds very
important to me is how this impacts workloads by default.
Andres is usually able to catch bottlenecks that everybody else is
unable to see, so perhaps checking with him the location of these
extra function calls would be a good first step. Your proposal goes
down to pgaio_io_stage(), pgaio_io_process_completion() and
pgaio_submit_staged() to track these counter increments.
--
Michael
Attachments:
[application/pgp-signature] signature.asc (833B, ../../[email protected]/2-signature.asc)
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^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-08 08:15 Bertrand Drouvot <[email protected]>
parent: Michael Paquier <[email protected]>
1 sibling, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-07-08 08:15 UTC (permalink / raw)
To: Michael Paquier <[email protected]>; +Cc: [email protected]; Andres Freund <[email protected]>
Hi,
On Wed, Jul 08, 2026 at 03:52:20PM +0900, Michael Paquier wrote:
> On Tue, Jul 07, 2026 at 11:02:03AM +0000, Bertrand Drouvot wrote:
> > 1/ pg_aios that lists all AIO handles that are currently in use. That shows
> > what's happening right now, but not what has happened.
> >
> > 2/ pg_stat_get_backend_io() that shows how much IO was done, but not how it
> > was done. There's no way to see whether IOs ran synchronously or
> > asynchronously, whether a backend was stalling on handle exhaustion, or how
> > completions are distributed across backends.
>
> While the information may be useful,
Thanks for looking at it!
> Andres is usually able to catch bottlenecks that everybody else is
> unable to see, so perhaps checking with him the location of these
> extra function calls would be a good first step. Your proposal goes
> down to pgaio_io_stage(), pgaio_io_process_completion() and
> pgaio_submit_staged() to track these counter increments.
yeah, and also to 1/ confirm that I did understand this area of the AIO code
correctly and 2/ see if other counters could make sense.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-08 18:08 Andres Freund <[email protected]>
parent: Michael Paquier <[email protected]>
1 sibling, 1 reply; 44+ messages in thread
From: Andres Freund @ 2026-07-08 18:08 UTC (permalink / raw)
To: Michael Paquier <[email protected]>; +Cc: Bertrand Drouvot <[email protected]>; [email protected]
Hi,
On 2026-07-08 15:52:20 +0900, Michael Paquier wrote:
> On Tue, Jul 07, 2026 at 11:02:03AM +0000, Bertrand Drouvot wrote:
> > 1/ pg_aios that lists all AIO handles that are currently in use. That shows
> > what's happening right now, but not what has happened.
> >
> > 2/ pg_stat_get_backend_io() that shows how much IO was done, but not how it
> > was done. There's no way to see whether IOs ran synchronously or
> > asynchronously, whether a backend was stalling on handle exhaustion, or how
> > completions are distributed across backends.
>
> While the information may be useful, one thing that sounds very
> important to me is how this impacts workloads by default.
> Andres is usually able to catch bottlenecks that everybody else is
> unable to see, so perhaps checking with him the location of these
> extra function calls would be a good first step. Your proposal goes
> down to pgaio_io_stage(), pgaio_io_process_completion() and
> pgaio_submit_staged() to track these counter increments.
I think the overhead might be ok, but I am rather doubtful that all of this
information is actually useful. You're adding quite a few counters for each
IO, do we actually need that?
E.g. what do we gain from counting:
- started (if you want to see the number of IOs that are in progress,
cumulative stats are the wrong tool)
- executed_async (that's just the number of IOs minus executed_sync)
- completed_self (that's just the number of IOs minus executed_other)
Separately, I'm doubtful it makes sense to have only per-backend stats for
this. I think you'd almost always want the stats for exited backend
(e.g. parallel workers) too.
Unfortunately I'm pretty doubtful that pgstat_backend.c is the right
architectural direction. It'll just end up implementing all kinds of stats,
since we'll incrementally want more and more per-backend stats. I think what
we'd want is rather something where for each applicable stats kind we have a
shared counter for all exited backends and then per-backend counters for live
backends, with helpers to aggregate the exited + live stats to a total.
Greetings,
Andres Freund
^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-09 04:19 Bertrand Drouvot <[email protected]>
parent: Andres Freund <[email protected]>
0 siblings, 1 reply; 44+ messages in thread
From: Bertrand Drouvot @ 2026-07-09 04:19 UTC (permalink / raw)
To: Andres Freund <[email protected]>; +Cc: Michael Paquier <[email protected]>; [email protected]
Hi,
On Wed, Jul 08, 2026 at 02:08:00PM -0400, Andres Freund wrote:
> Hi,
>
> On 2026-07-08 15:52:20 +0900, Michael Paquier wrote:
> > On Tue, Jul 07, 2026 at 11:02:03AM +0000, Bertrand Drouvot wrote:
> > > 1/ pg_aios that lists all AIO handles that are currently in use. That shows
> > > what's happening right now, but not what has happened.
> > >
> > > 2/ pg_stat_get_backend_io() that shows how much IO was done, but not how it
> > > was done. There's no way to see whether IOs ran synchronously or
> > > asynchronously, whether a backend was stalling on handle exhaustion, or how
> > > completions are distributed across backends.
> >
> > While the information may be useful, one thing that sounds very
> > important to me is how this impacts workloads by default.
>
>
> > Andres is usually able to catch bottlenecks that everybody else is
> > unable to see, so perhaps checking with him the location of these
> > extra function calls would be a good first step. Your proposal goes
> > down to pgaio_io_stage(), pgaio_io_process_completion() and
> > pgaio_submit_staged() to track these counter increments.
>
> I think the overhead might be ok,
Thanks for the feedback.
> but I am rather doubtful that all of this
> information is actually useful. You're adding quite a few counters for each
> IO, do we actually need that?
>
> E.g. what do we gain from counting:
> - started (if you want to see the number of IOs that are in progress,
> cumulative stats are the wrong tool)
> - executed_async (that's just the number of IOs minus executed_sync)
> - completed_self (that's just the number of IOs minus executed_other)
Yeah, we can remove some fields (as they're derivable).
> Separately, I'm doubtful it makes sense to have only per-backend stats for
> this. I think you'd almost always want the stats for exited backend
> (e.g. parallel workers) too.
Indeed, adding a global view would capture their activity.
> Unfortunately I'm pretty doubtful that pgstat_backend.c is the right
> architectural direction. It'll just end up implementing all kinds of stats,
> since we'll incrementally want more and more per-backend stats. I think what
> we'd want is rather something where for each applicable stats kind we have a
> shared counter for all exited backends and then per-backend counters for live
> backends, with helpers to aggregate the exited + live stats to a total.
That's a very nice proposal that would avoid the double counting. OTOH, that's
also a major re-design that would benefit all existing per-backend stats kinds.
I can see 2 options:
1/
step 1: Implement per-backend AIO stats (like proposed taking into account your
remark about useless, derivable fields) + a global view.
step 2: work on the re-design
2/
step 1: work on the redesign
step 2: Add AIO stats based on the re-design
The pros of 1/ is that step 1 would most probably land in 20, providing more user
visibility (+ it could be used or improved during the AIO write project). Step 2
is a much larger project that might not land in 20.
The cons, would be double counting (as there is no need to try to implement
something like [1] as we are going to re-design anyway).
I'll be tempted to vote for 1/ to provide faster added value. What do you (Andres,
Michael) think?
[1]: https://postgr.es/m/[email protected]
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 44+ messages in thread
* Re: Add per-backend AIO statistics
@ 2026-07-10 04:56 Bertrand Drouvot <[email protected]>
parent: Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 44+ messages in thread
From: Bertrand Drouvot @ 2026-07-10 04:56 UTC (permalink / raw)
To: Andres Freund <[email protected]>; +Cc: Michael Paquier <[email protected]>; [email protected]
Hi,
On Thu, Jul 09, 2026 at 04:19:26AM +0000, Bertrand Drouvot wrote:
> Hi,
>
> On Wed, Jul 08, 2026 at 02:08:00PM -0400, Andres Freund wrote:
>
> > Unfortunately I'm pretty doubtful that pgstat_backend.c is the right
> > architectural direction. It'll just end up implementing all kinds of stats,
> > since we'll incrementally want more and more per-backend stats. I think what
> > we'd want is rather something where for each applicable stats kind we have a
> > shared counter for all exited backends and then per-backend counters for live
> > backends, with helpers to aggregate the exited + live stats to a total.
>
> That's a very nice proposal that would avoid the double counting. OTOH, that's
> also a major re-design that would benefit all existing per-backend stats kinds.
>
> I can see 2 options:
>
> 1/
>
> step 1: Implement per-backend AIO stats (like proposed taking into account your
> remark about useless, derivable fields) + a global view.
> step 2: work on the re-design
>
> 2/
>
> step 1: work on the redesign
> step 2: Add AIO stats based on the re-design
>
> The pros of 1/ is that step 1 would most probably land in 20, providing more user
> visibility (+ it could be used or improved during the AIO write project). Step 2
> is a much larger project that might not land in 20.
>
> The cons, would be double counting (as there is no need to try to implement
> something like [1] as we are going to re-design anyway).
>
> I'll be tempted to vote for 1/ to provide faster added value. What do you (Andres,
> Michael) think?
Actually, there is no rush to merge the per-backend AIO stats (we still have
plenty of time for 20). So let's try option 2 and implement the new design first
and see where it goes. I'll create a dedicated thread once ready.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 44+ messages in thread
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2025-07-26 17:57 [PATCH v25 1/4] Add REPACK command Álvaro Herrera <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-06-11 09:45 [PATCH v1] Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-07-07 11:02 Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-07-08 06:00 ` Re: Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-07-08 06:52 ` Re: Add per-backend AIO statistics Michael Paquier <[email protected]>
2026-07-08 08:15 ` Re: Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-07-08 18:08 ` Re: Add per-backend AIO statistics Andres Freund <[email protected]>
2026-07-09 04:19 ` Re: Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
2026-07-10 04:56 ` Re: Add per-backend AIO statistics Bertrand Drouvot <[email protected]>
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