diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/lmgr/predicate.c | 48 | ||||
| -rw-r--r-- | src/backend/utils/misc/guc.c | 22 | ||||
| -rw-r--r-- | src/backend/utils/misc/postgresql.conf.sample | 4 | ||||
| -rw-r--r-- | src/include/storage/predicate.h | 2 |
4 files changed, 59 insertions, 17 deletions
diff --git a/src/backend/storage/lmgr/predicate.c b/src/backend/storage/lmgr/predicate.c index 7aa719d6123..10bac71e94b 100644 --- a/src/backend/storage/lmgr/predicate.c +++ b/src/backend/storage/lmgr/predicate.c @@ -352,8 +352,15 @@ static OldSerXidControl oldSerXidControl; static SERIALIZABLEXACT *OldCommittedSxact; -/* This configuration variable is used to set the predicate lock table size */ +/* + * These configuration variables are used to set the predicate lock table size + * and to control promotion of predicate locks to coarser granularity in an + * attempt to degrade performance (mostly as false positive serialization + * failure) gracefully in the face of memory pressurel + */ int max_predicate_locks_per_xact; /* set by guc.c */ +int max_predicate_locks_per_relation; /* set by guc.c */ +int max_predicate_locks_per_page; /* set by guc.c */ /* * This provides a list of objects in order to track transactions @@ -437,7 +444,7 @@ static void RestoreScratchTarget(bool lockheld); static void RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target, uint32 targettaghash); static void DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag); -static int PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag); +static int MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag); static bool CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag); static void DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag); static void CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag, @@ -2118,28 +2125,35 @@ DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag) } /* - * Returns the promotion threshold for a given predicate lock - * target. This is the number of descendant locks required to promote - * to the specified tag. Note that the threshold includes non-direct - * descendants, e.g. both tuples and pages for a relation lock. + * Returns the promotion limit for a given predicate lock target. This is the + * max number of descendant locks allowed before promoting to the specified + * tag. Note that the limit includes non-direct descendants (e.g., both tuples + * and pages for a relation lock). + * + * Currently the default limit is 2 for a page lock, and half of the value of + * max_pred_locks_per_transaction - 1 for a relation lock, to match behavior + * of earlier releases when upgrading. * - * TODO SSI: We should do something more intelligent about what the - * thresholds are, either making it proportional to the number of - * tuples in a page & pages in a relation, or at least making it a - * GUC. Currently the threshold is 3 for a page lock, and - * max_pred_locks_per_transaction/2 for a relation lock, chosen - * entirely arbitrarily (and without benchmarking). + * TODO SSI: We should probably add additional GUCs to allow a maximum ratio + * of page and tuple locks based on the pages in a relation, and the maximum + * ratio of tuple locks to tuples in a page. This would provide more + * generally "balanced" allocation of locks to where they are most useful, + * while still allowing the absolute numbers to prevent one relation from + * tying up all predicate lock resources. */ static int -PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag) +MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag) { switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag)) { case PREDLOCKTAG_RELATION: - return max_predicate_locks_per_xact / 2; + return max_predicate_locks_per_relation < 0 + ? (max_predicate_locks_per_xact + / (-max_predicate_locks_per_relation)) - 1 + : max_predicate_locks_per_relation; case PREDLOCKTAG_PAGE: - return 3; + return max_predicate_locks_per_page; case PREDLOCKTAG_TUPLE: @@ -2194,8 +2208,8 @@ CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag) else parentlock->childLocks++; - if (parentlock->childLocks >= - PredicateLockPromotionThreshold(&targettag)) + if (parentlock->childLocks > + MaxPredicateChildLocks(&targettag)) { /* * We should promote to this parent lock. Continue to check its diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c index a57b175b2d3..19d258d0336 100644 --- a/src/backend/utils/misc/guc.c +++ b/src/backend/utils/misc/guc.c @@ -2200,6 +2200,28 @@ static struct config_int ConfigureNamesInt[] = }, { + {"max_pred_locks_per_relation", PGC_SIGHUP, LOCK_MANAGEMENT, + gettext_noop("Sets the maximum number of predicate-locked pages and tuples per relation."), + gettext_noop("If more than this total of pages and tuples in the same relation are locked " + "by a connection, those locks are replaced by a relation level lock.") + }, + &max_predicate_locks_per_relation, + -2, INT_MIN, INT_MAX, + NULL, NULL, NULL + }, + + { + {"max_pred_locks_per_page", PGC_SIGHUP, LOCK_MANAGEMENT, + gettext_noop("Sets the maximum number of predicate-locked tuples per page."), + gettext_noop("If more than this number of tuples on the same page are locked " + "by a connection, those locks are replaced by a page level lock.") + }, + &max_predicate_locks_per_page, + 2, 0, INT_MAX, + NULL, NULL, NULL + }, + + { {"authentication_timeout", PGC_SIGHUP, CONN_AUTH_SECURITY, gettext_noop("Sets the maximum allowed time to complete client authentication."), NULL, diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 8a93bdcb3f0..512be0a92ed 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -593,6 +593,10 @@ # (change requires restart) #max_pred_locks_per_transaction = 64 # min 10 # (change requires restart) +#max_pred_locks_per_relation = -2 # negative values mean + # (max_pred_locks_per_transaction + # / -max_pred_locks_per_relation) - 1 +#max_pred_locks_per_page = 2 # min 0 #------------------------------------------------------------------------------ diff --git a/src/include/storage/predicate.h b/src/include/storage/predicate.h index f996d8e8181..8f9ea29917b 100644 --- a/src/include/storage/predicate.h +++ b/src/include/storage/predicate.h @@ -22,6 +22,8 @@ * GUC variables */ extern int max_predicate_locks_per_xact; +extern int max_predicate_locks_per_relation; +extern int max_predicate_locks_per_page; /* Number of SLRU buffers to use for predicate locking */ |