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help / color / mirror / Atom feedFrom: Kyotaro Horiguchi <[email protected]>
Subject: [PATCH v6 1/3] CatCache expiration feature
Date: Wed, 18 Nov 2020 16:54:31 +0900
---
src/backend/access/transam/xact.c | 3 ++
src/backend/utils/cache/catcache.c | 87 +++++++++++++++++++++++++++++-
src/backend/utils/misc/guc.c | 12 +++++
src/include/utils/catcache.h | 19 +++++++
4 files changed, 120 insertions(+), 1 deletion(-)
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index a2068e3fd4..86888d2409 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1086,6 +1086,9 @@ static void
AtStart_Cache(void)
{
AcceptInvalidationMessages();
+
+ if (xactStartTimestamp != 0)
+ SetCatCacheClock(xactStartTimestamp);
}
/*
diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c
index fa2b49c676..644d92dd9a 100644
--- a/src/backend/utils/cache/catcache.c
+++ b/src/backend/utils/cache/catcache.c
@@ -38,6 +38,7 @@
#include "utils/rel.h"
#include "utils/resowner_private.h"
#include "utils/syscache.h"
+#include "utils/timestamp.h"
/* #define CACHEDEBUG */ /* turns DEBUG elogs on */
@@ -60,9 +61,19 @@
#define CACHE_elog(...)
#endif
+/*
+ * GUC variable to define the minimum age of entries that will be considered
+ * to be evicted in seconds. -1 to disable the feature.
+ */
+int catalog_cache_prune_min_age = -1;
+uint64 prune_min_age_us;
+
/* Cache management header --- pointer is NULL until created */
static CatCacheHeader *CacheHdr = NULL;
+/* Clock for the last accessed time of a catcache entry. */
+uint64 catcacheclock = 0;
+
static inline HeapTuple SearchCatCacheInternal(CatCache *cache,
int nkeys,
Datum v1, Datum v2,
@@ -74,6 +85,7 @@ static pg_noinline HeapTuple SearchCatCacheMiss(CatCache *cache,
Index hashIndex,
Datum v1, Datum v2,
Datum v3, Datum v4);
+static bool CatCacheCleanupOldEntries(CatCache *cp);
static uint32 CatalogCacheComputeHashValue(CatCache *cache, int nkeys,
Datum v1, Datum v2, Datum v3, Datum v4);
@@ -99,6 +111,15 @@ static void CatCacheFreeKeys(TupleDesc tupdesc, int nkeys, int *attnos,
static void CatCacheCopyKeys(TupleDesc tupdesc, int nkeys, int *attnos,
Datum *srckeys, Datum *dstkeys);
+/* GUC assign function */
+void
+assign_catalog_cache_prune_min_age(int newval, void *extra)
+{
+ if (newval < 0)
+ prune_min_age_us = UINT64_MAX;
+ else
+ prune_min_age_us = ((uint64) newval) * USECS_PER_SEC;
+}
/*
* internal support functions
@@ -1264,6 +1285,9 @@ SearchCatCacheInternal(CatCache *cache,
*/
dlist_move_head(bucket, &ct->cache_elem);
+ /* Record the last access timestamp */
+ ct->lastaccess = catcacheclock;
+
/*
* If it's a positive entry, bump its refcount and return it. If it's
* negative, we can report failure to the caller.
@@ -1425,6 +1449,61 @@ SearchCatCacheMiss(CatCache *cache,
return &ct->tuple;
}
+/*
+ * CatCacheCleanupOldEntries - Remove infrequently-used entries
+ *
+ * Catcache entries happen to be left unused for a long time for several
+ * reasons. Remove such entries to prevent catcache from bloating. It is based
+ * on the similar algorithm with buffer eviction. Entries that are accessed
+ * several times in a certain period live longer than those that have had less
+ * access in the same duration.
+ */
+static bool
+CatCacheCleanupOldEntries(CatCache *cp)
+{
+ int nremoved = 0;
+ int i;
+ long oldest_ts = catcacheclock;
+ uint64 prune_threshold = catcacheclock - prune_min_age_us;
+
+ /* Scan over the whole hash to find entries to remove */
+ for (i = 0 ; i < cp->cc_nbuckets ; i++)
+ {
+ dlist_mutable_iter iter;
+
+ dlist_foreach_modify(iter, &cp->cc_bucket[i])
+ {
+ CatCTup *ct = dlist_container(CatCTup, cache_elem, iter.cur);
+
+ /* Don't remove referenced entries */
+ if (ct->refcount == 0 &&
+ (ct->c_list == NULL || ct->c_list->refcount == 0))
+ {
+ if (ct->lastaccess < prune_threshold)
+ {
+ CatCacheRemoveCTup(cp, ct);
+ nremoved++;
+
+ /* don't let the removed entry update oldest_ts */
+ continue;
+ }
+ }
+
+ /* update the oldest timestamp if the entry remains alive */
+ if (ct->lastaccess < oldest_ts)
+ oldest_ts = ct->lastaccess;
+ }
+ }
+
+ cp->cc_oldest_ts = oldest_ts;
+
+ if (nremoved > 0)
+ elog(DEBUG1, "pruning catalog cache id=%d for %s: removed %d / %d",
+ cp->id, cp->cc_relname, nremoved, cp->cc_ntup + nremoved);
+
+ return nremoved > 0;
+}
+
/*
* ReleaseCatCache
*
@@ -1888,6 +1967,7 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments,
ct->dead = false;
ct->negative = negative;
ct->hash_value = hashValue;
+ ct->lastaccess = catcacheclock;
dlist_push_head(&cache->cc_bucket[hashIndex], &ct->cache_elem);
@@ -1899,7 +1979,12 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments,
* arbitrarily, we enlarge when fill factor > 2.
*/
if (cache->cc_ntup > cache->cc_nbuckets * 2)
- RehashCatCache(cache);
+ {
+ /* try removing old entries before expanding hash */
+ if (catcacheclock - cache->cc_oldest_ts < prune_min_age_us ||
+ !CatCacheCleanupOldEntries(cache))
+ RehashCatCache(cache);
+ }
return ct;
}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 17579eeaca..255e9fa73d 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -88,6 +88,7 @@
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
+#include "utils/catcache.h"
#include "utils/float.h"
#include "utils/guc_tables.h"
#include "utils/memutils.h"
@@ -3445,6 +3446,17 @@ static struct config_int ConfigureNamesInt[] =
NULL, NULL, NULL
},
+ {
+ {"catalog_cache_prune_min_age", PGC_USERSET, RESOURCES_MEM,
+ gettext_noop("System catalog cache entries that are living unused more than this seconds are considered for removal."),
+ gettext_noop("The value of -1 turns off pruning."),
+ GUC_UNIT_S
+ },
+ &catalog_cache_prune_min_age,
+ -1, -1, INT_MAX,
+ NULL, assign_catalog_cache_prune_min_age, NULL
+ },
+
/* End-of-list marker */
{
{NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL, NULL
diff --git a/src/include/utils/catcache.h b/src/include/utils/catcache.h
index ddc2762eb3..291e857e38 100644
--- a/src/include/utils/catcache.h
+++ b/src/include/utils/catcache.h
@@ -22,6 +22,7 @@
#include "access/htup.h"
#include "access/skey.h"
+#include "datatype/timestamp.h"
#include "lib/ilist.h"
#include "utils/relcache.h"
@@ -61,6 +62,7 @@ typedef struct catcache
slist_node cc_next; /* list link */
ScanKeyData cc_skey[CATCACHE_MAXKEYS]; /* precomputed key info for heap
* scans */
+ uint64 cc_oldest_ts; /* timestamp (us) of the oldest tuple */
/*
* Keep these at the end, so that compiling catcache.c with CATCACHE_STATS
@@ -119,6 +121,7 @@ typedef struct catctup
bool dead; /* dead but not yet removed? */
bool negative; /* negative cache entry? */
HeapTupleData tuple; /* tuple management header */
+ uint64 lastaccess; /* timestamp in us of the last usage */
/*
* The tuple may also be a member of at most one CatCList. (If a single
@@ -189,6 +192,22 @@ typedef struct catcacheheader
/* this extern duplicates utils/memutils.h... */
extern PGDLLIMPORT MemoryContext CacheMemoryContext;
+
+/* for guc.c, not PGDLLPMPORT'ed */
+extern int catalog_cache_prune_min_age;
+
+/* source clock for access timestamp of catcache entries */
+extern uint64 catcacheclock;
+
+/* SetCatCacheClock - set catcache timestamp source clock */
+static inline void
+SetCatCacheClock(TimestampTz ts)
+{
+ catcacheclock = (uint64) ts;
+}
+
+extern void assign_catalog_cache_prune_min_age(int newval, void *extra);
+
extern void CreateCacheMemoryContext(void);
extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
--
2.27.0
----Next_Part(Thu_Jan_14_17_32_27_2021_995)--
Content-Type: Text/X-Patch; charset=us-ascii
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="v6-0002-Remove-dead-flag-from-catcache-tuple.patch"
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