From 705b67a79ef7e27a450083944f8d970b7eb9e619 Mon Sep 17 00:00:00 2001 From: Kyotaro Horiguchi Date: Tue, 26 Dec 2017 17:43:09 +0900 Subject: [PATCH 1/3] Remove entries that haven't been used for a certain time Catcache entries can be left alone for several reasons. It is not desirable that they eat up memory. With this patch, This adds consideration of removal of entries that haven't been used for a certain time before enlarging the hash array. --- doc/src/sgml/config.sgml | 38 +++++++ src/backend/access/transam/xact.c | 3 + src/backend/utils/cache/catcache.c | 152 +++++++++++++++++++++++++- src/backend/utils/misc/guc.c | 23 ++++ src/backend/utils/misc/postgresql.conf.sample | 2 + src/include/utils/catcache.h | 19 ++++ 6 files changed, 233 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 3a8fc7d803..394e0703f8 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1557,6 +1557,44 @@ include_dir 'conf.d' + + syscache_memory_target (integer) + + syscache_memory_target configuration parameter + + + + + Specifies the maximum amount of memory to which syscache is expanded + without pruning. The value defaults to 0, indicating that pruning is + always considered. After exceeding this size, syscache pruning is + considered according to + . If you need to keep + certain amount of syscache entries with intermittent usage, try + increase this setting. + + + + + + syscache_prune_min_age (integer) + + syscache_prune_min_age configuration parameter + + + + + Specifies the minimum amount of unused time in seconds at which a + syscache entry is considered to be removed. -1 indicates that syscache + pruning is disabled at all. The value defaults to 600 seconds + (10 minutes). The syscache entries that are not + used for the duration can be removed to prevent syscache bloat. This + behavior is suppressed until the size of syscache exceeds + . + + + + max_stack_depth (integer) diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index dbaaf8e005..86d76917bb 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -733,6 +733,9 @@ void SetCurrentStatementStartTimestamp(void) { stmtStartTimestamp = GetCurrentTimestamp(); + + /* Set this timestamp as aproximated current time */ + SetCatCacheClock(stmtStartTimestamp); } /* diff --git a/src/backend/utils/cache/catcache.c b/src/backend/utils/cache/catcache.c index 5ddbf6eab1..0236a05127 100644 --- a/src/backend/utils/cache/catcache.c +++ b/src/backend/utils/cache/catcache.c @@ -71,9 +71,23 @@ #define CACHE6_elog(a,b,c,d,e,f,g) #endif +/* + * GUC variable to define the minimum size of hash to cosider entry eviction. + * Let the name be the same with the guc variable name, not using 'catcache'. + */ +int syscache_memory_target = 0; + +/* GUC variable to define the minimum age of entries that will be cosidered + * to be evicted in seconds. Ditto for the name. + */ +int syscache_prune_min_age = 600; + /* Cache management header --- pointer is NULL until created */ static CatCacheHeader *CacheHdr = NULL; +/* Timestamp used for any operation on caches. */ +TimestampTz catcacheclock = 0; + static inline HeapTuple SearchCatCacheInternal(CatCache *cache, int nkeys, Datum v1, Datum v2, @@ -866,9 +880,130 @@ InitCatCache(int id, */ MemoryContextSwitchTo(oldcxt); + /* initilize catcache reference clock if haven't done yet */ + if (catcacheclock == 0) + catcacheclock = GetCurrentTimestamp(); + return cp; } +/* + * CatCacheCleanupOldEntries - Remove infrequently-used entries + * + * Catcache entries can be left alone for several reasons. We remove them if + * they not accessed for a certain time to prevent catcache from bloating. The + * eviction is performed with the similar algorithm with buffer eviction using + * access counter. Entries that are accessed several times can live longer + * than those that have had no access in the same duration. + */ +static bool +CatCacheCleanupOldEntries(CatCache *cp) +{ + int i; + int nremoved = 0; + size_t hash_size; +#ifdef CATCACHE_STATS + /* These variables are only for debugging purpose */ + int ntotal = 0; + /* + * nth element in nentries stores the number of cache entries that have + * lived unaccessed for corresponding multiple in ageclass of + * syscache_prune_min_age. The index of nremoved_entry is the value of the + * clock-sweep counter, which takes from 0 up to 2. + */ + double ageclass[] = {0.05, 0.1, 1.0, 2.0, 3.0, 0.0}; + int nentries[] = {0, 0, 0, 0, 0, 0}; + int nremoved_entry[3] = {0, 0, 0}; + int j; +#endif + + /* Return immediately if no pruning is wanted */ + if (syscache_prune_min_age < 0) + return false; + + /* + * Return without pruning if the size of the hash is below the target. + * Since the area for bucket array is dominant, consider only it. + */ + hash_size = cp->cc_nbuckets * sizeof(dlist_head); + if (hash_size < (Size) syscache_memory_target * 1024L) + return false; + + /* Search the whole hash for 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); + long entry_age; + int us; + + + /* + * Calculate the duration from the time of the last access to the + * "current" time. Since catcacheclock is not advanced within a + * transaction, the entries that are accessed within the current + * transaction won't be pruned. + */ + TimestampDifference(ct->lastaccess, catcacheclock, &entry_age, &us); + +#ifdef CATCACHE_STATS + /* count catcache entries for each age class */ + ntotal++; + for (j = 0 ; + ageclass[j] != 0.0 && + entry_age > syscache_prune_min_age * ageclass[j] ; + j++); + if (ageclass[j] == 0.0) j--; + nentries[j]++; +#endif + + /* + * Try to remove entries older than syscache_prune_min_age + * seconds. Entries that are not accessed after last pruning are + * removed in that seconds, and that has been accessed several + * times are removed after leaving alone for up to three times of + * the duration. We don't try shrink buckets since pruning + * effectively caps catcache expansion in the long term. + */ + if (entry_age > syscache_prune_min_age) + { +#ifdef CATCACHE_STATS + Assert (ct->naccess >= 0 && ct->naccess <= 2); + nremoved_entry[ct->naccess]++; +#endif + if (ct->naccess > 0) + ct->naccess--; + else + { + if (!ct->c_list || ct->c_list->refcount == 0) + { + CatCacheRemoveCTup(cp, ct); + nremoved++; + } + } + } + } + } + +#ifdef CATCACHE_STATS + ereport(DEBUG1, + (errmsg ("removed %d/%d, age(-%.0fs:%d, -%.0fs:%d, *-%.0fs:%d, -%.0fs:%d, -%.0fs:%d) naccessed(0:%d, 1:%d, 2:%d)", + nremoved, ntotal, + ageclass[0] * syscache_prune_min_age, nentries[0], + ageclass[1] * syscache_prune_min_age, nentries[1], + ageclass[2] * syscache_prune_min_age, nentries[2], + ageclass[3] * syscache_prune_min_age, nentries[3], + ageclass[4] * syscache_prune_min_age, nentries[4], + nremoved_entry[0], nremoved_entry[1], nremoved_entry[2]), + errhidestmt(true))); +#endif + + return nremoved > 0; +} + /* * Enlarge a catcache, doubling the number of buckets. */ @@ -1282,6 +1417,11 @@ SearchCatCacheInternal(CatCache *cache, */ dlist_move_head(bucket, &ct->cache_elem); + /* Update access information for pruning */ + if (ct->naccess < 2) + ct->naccess++; + 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. @@ -1813,7 +1953,6 @@ ReleaseCatCacheList(CatCList *list) CatCacheRemoveCList(list->my_cache, list); } - /* * CatalogCacheCreateEntry * Create a new CatCTup entry, copying the given HeapTuple and other @@ -1906,6 +2045,8 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments, ct->dead = false; ct->negative = negative; ct->hash_value = hashValue; + ct->naccess = 0; + ct->lastaccess = catcacheclock; dlist_push_head(&cache->cc_bucket[hashIndex], &ct->cache_elem); @@ -1913,10 +2054,13 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, Datum *arguments, CacheHdr->ch_ntup++; /* - * If the hash table has become too full, enlarge the buckets array. Quite - * arbitrarily, we enlarge when fill factor > 2. + * If the hash table has become too full, try cleanup by removing + * infrequently used entries to make a room for the new entry. If it + * failed, enlarge the bucket array instead. Quite arbitrarily, we try + * this when fill factor > 2. */ - if (cache->cc_ntup > cache->cc_nbuckets * 2) + if (cache->cc_ntup > cache->cc_nbuckets * 2 && + !CatCacheCleanupOldEntries(cache)) RehashCatCache(cache); return ct; diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index a4f9b3668e..5e0d18657f 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -78,6 +78,7 @@ #include "tsearch/ts_cache.h" #include "utils/builtins.h" #include "utils/bytea.h" +#include "utils/catcache.h" #include "utils/guc_tables.h" #include "utils/memutils.h" #include "utils/pg_locale.h" @@ -1972,6 +1973,28 @@ static struct config_int ConfigureNamesInt[] = NULL, NULL, NULL }, + { + {"syscache_memory_target", PGC_USERSET, RESOURCES_MEM, + gettext_noop("Sets the minimum syscache size to keep."), + gettext_noop("Syscache is not pruned before exceeding this size."), + GUC_UNIT_KB + }, + &syscache_memory_target, + 0, 0, MAX_KILOBYTES, + NULL, NULL, NULL + }, + + { + {"syscache_prune_min_age", PGC_USERSET, RESOURCES_MEM, + gettext_noop("Sets the minimum duration of an unused syscache entry to remove."), + gettext_noop("Syscache entries that live unused for longer than this seconds are considered to be removed."), + GUC_UNIT_S + }, + &syscache_prune_min_age, + 600, -1, INT_MAX, + NULL, NULL, NULL + }, + /* * We use the hopefully-safely-small value of 100kB as the compiled-in * default for max_stack_depth. InitializeGUCOptions will increase it if diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 39272925fb..5a5729a88f 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -124,6 +124,8 @@ #work_mem = 4MB # min 64kB #maintenance_work_mem = 64MB # min 1MB #autovacuum_work_mem = -1 # min 1MB, or -1 to use maintenance_work_mem +#syscache_memory_target = 0kB # in kB. zero disables the feature +#syscache_prune_min_age = 600s # -1 disables the feature #max_stack_depth = 2MB # min 100kB #dynamic_shared_memory_type = posix # the default is the first option # supported by the operating system: diff --git a/src/include/utils/catcache.h b/src/include/utils/catcache.h index 7b22f9c7bc..c3c4d65998 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" @@ -119,6 +120,8 @@ typedef struct catctup bool dead; /* dead but not yet removed? */ bool negative; /* negative cache entry? */ HeapTupleData tuple; /* tuple management header */ + int naccess; /* # of access to this entry, up to 2 */ + TimestampTz lastaccess; /* approx. timestamp 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 syscache_prune_min_age; +extern int syscache_memory_target; + +/* to use as access timestamp of catcache entries */ +extern TimestampTz catcacheclock; + +/* + * SetCatCacheClock - set timestamp for catcache access record + */ +static inline void +SetCatCacheClock(TimestampTz ts) +{ + catcacheclock = ts; +} + extern void CreateCacheMemoryContext(void); extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid, -- 2.16.2