From 5f318170b9c1e0caa1033862261800f06135e5bd Mon Sep 17 00:00:00 2001 From: Kyotaro Horiguchi Date: Wed, 18 Nov 2020 16:54:31 +0900 Subject: [PATCH v7 1/3] CatCache expiration feature --- 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