diff options
Diffstat (limited to 'src/backend')
| -rw-r--r-- | src/backend/storage/lmgr/lock.c | 5 | ||||
| -rw-r--r-- | src/backend/utils/init/postinit.c | 34 |
2 files changed, 19 insertions, 20 deletions
diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c index 002303664aa..86b06b9223f 100644 --- a/src/backend/storage/lmgr/lock.c +++ b/src/backend/storage/lmgr/lock.c @@ -210,9 +210,12 @@ int FastPathLockGroupsPerBackend = 0; * * The selected constant (49157) is a prime not too close to 2^k, and it's * small enough to not cause overflows (in 64-bit). + * + * We can assume that FastPathLockGroupsPerBackend is a power-of-two per + * InitializeFastPathLocks(). */ #define FAST_PATH_REL_GROUP(rel) \ - (((uint64) (rel) * 49157) % FastPathLockGroupsPerBackend) + (((uint64) (rel) * 49157) & (FastPathLockGroupsPerBackend - 1)) /* * Given the group/slot indexes, calculate the slot index in the whole array diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c index 01309ef3f86..28f09a27001 100644 --- a/src/backend/utils/init/postinit.c +++ b/src/backend/utils/init/postinit.c @@ -575,13 +575,6 @@ InitializeMaxBackends(void) * * This must be called after modules have had the chance to alter GUCs in * shared_preload_libraries and before shared memory size is determined. - * - * The default max_locks_per_xact=64 means 4 groups by default. - * - * We allow anything between 1 and 1024 groups, with the usual power-of-2 - * logic. The 1 is the "old" size with only 16 slots, 1024 is an arbitrary - * limit (matching max_locks_per_xact = 16k). Values over 1024 are unlikely - * to be beneficial - there are bottlenecks we'll hit way before that. */ void InitializeFastPathLocks(void) @@ -589,19 +582,22 @@ InitializeFastPathLocks(void) /* Should be initialized only once. */ Assert(FastPathLockGroupsPerBackend == 0); - /* we need at least one group */ - FastPathLockGroupsPerBackend = 1; - - while (FastPathLockGroupsPerBackend < FP_LOCK_GROUPS_PER_BACKEND_MAX) - { - /* stop once we exceed max_locks_per_xact */ - if (FastPathLockSlotsPerBackend() >= max_locks_per_xact) - break; - - FastPathLockGroupsPerBackend *= 2; - } + /* + * Based on the max_locks_per_transaction GUC, as that's a good indicator + * of the expected number of locks, figure out the value for + * FastPathLockGroupsPerBackend. This must be a power-of-two. We cap the + * value at FP_LOCK_GROUPS_PER_BACKEND_MAX and insist the value is at + * least 1. + * + * The default max_locks_per_transaction = 64 means 4 groups by default. + */ + FastPathLockGroupsPerBackend = + Max(Min(pg_nextpower2_32(max_locks_per_xact) / FP_LOCK_SLOTS_PER_GROUP, + FP_LOCK_GROUPS_PER_BACKEND_MAX), 1); - Assert(FastPathLockGroupsPerBackend <= FP_LOCK_GROUPS_PER_BACKEND_MAX); + /* Validate we did get a power-of-two */ + Assert(FastPathLockGroupsPerBackend == + pg_nextpower2_32(FastPathLockGroupsPerBackend)); } /* |