From b33d6101c912d1d6ce77cf5d95161ba0b6c10874 Mon Sep 17 00:00:00 2001 From: Bertrand Drouvot Date: Tue, 29 Jul 2025 08:36:35 +0000 Subject: [PATCH v5 1/2] Add lock statistics Adding a new stat kind PGSTAT_KIND_LOCK for the lock statistics. This new statistic kind is a fixed one because its key is the lock type so that we know its size is LOCKTAG_LAST_TYPE + 1. This statistic kind records the following counters: waits wait_time fastpath_exceeded The waits and wait_time counters are incremented if log_lock_waits is on and the session waited longer than deadlock_timeout to acquire the lock. No extra details is added (like the ones, i.e relation oid, database oid, we can find in pg_locks). The idea is to provide an idea on what the locking behaviour looks like. XXX: Bump stat file format --- src/backend/storage/lmgr/lock.c | 58 ++++---- src/backend/storage/lmgr/proc.c | 6 + src/backend/utils/activity/Makefile | 1 + src/backend/utils/activity/meson.build | 1 + src/backend/utils/activity/pgstat.c | 18 +++ src/backend/utils/activity/pgstat_lock.c | 162 +++++++++++++++++++++++ src/include/pgstat.h | 28 ++++ src/include/utils/pgstat_internal.h | 21 +++ src/include/utils/pgstat_kind.h | 5 +- src/tools/pgindent/typedefs.list | 4 + 10 files changed, 276 insertions(+), 28 deletions(-) 28.9% src/backend/storage/lmgr/ 54.5% src/backend/utils/activity/ 7.4% src/include/utils/ 8.2% src/include/ diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c index e1168ad3837..8a0d970b26b 100644 --- a/src/backend/storage/lmgr/lock.c +++ b/src/backend/storage/lmgr/lock.c @@ -39,6 +39,7 @@ #include "access/xlogutils.h" #include "miscadmin.h" #include "pg_trace.h" +#include "pgstat.h" #include "storage/lmgr.h" #include "storage/proc.h" #include "storage/procarray.h" @@ -984,37 +985,42 @@ LockAcquireExtended(const LOCKTAG *locktag, * lock type on a relation we have already locked using the fast-path, but * for now we don't worry about that case either. */ - if (EligibleForRelationFastPath(locktag, lockmode) && - FastPathLocalUseCounts[FAST_PATH_REL_GROUP(locktag->locktag_field2)] < FP_LOCK_SLOTS_PER_GROUP) + if (EligibleForRelationFastPath(locktag, lockmode)) { - uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode); - bool acquired; - - /* - * LWLockAcquire acts as a memory sequencing point, so it's safe to - * assume that any strong locker whose increment to - * FastPathStrongRelationLocks->counts becomes visible after we test - * it has yet to begin to transfer fast-path locks. - */ - LWLockAcquire(&MyProc->fpInfoLock, LW_EXCLUSIVE); - if (FastPathStrongRelationLocks->count[fasthashcode] != 0) - acquired = false; - else - acquired = FastPathGrantRelationLock(locktag->locktag_field2, - lockmode); - LWLockRelease(&MyProc->fpInfoLock); - if (acquired) + if (FastPathLocalUseCounts[FAST_PATH_REL_GROUP(locktag->locktag_field2)] < + FP_LOCK_SLOTS_PER_GROUP) { + uint32 fasthashcode = FastPathStrongLockHashPartition(hashcode); + bool acquired; + /* - * The locallock might contain stale pointers to some old shared - * objects; we MUST reset these to null before considering the - * lock to be acquired via fast-path. + * LWLockAcquire acts as a memory sequencing point, so it's safe + * to assume that any strong locker whose increment to + * FastPathStrongRelationLocks->counts becomes visible after we + * test it has yet to begin to transfer fast-path locks. */ - locallock->lock = NULL; - locallock->proclock = NULL; - GrantLockLocal(locallock, owner); - return LOCKACQUIRE_OK; + LWLockAcquire(&MyProc->fpInfoLock, LW_EXCLUSIVE); + if (FastPathStrongRelationLocks->count[fasthashcode] != 0) + acquired = false; + else + acquired = FastPathGrantRelationLock(locktag->locktag_field2, + lockmode); + LWLockRelease(&MyProc->fpInfoLock); + if (acquired) + { + /* + * The locallock might contain stale pointers to some old + * shared objects; we MUST reset these to null before + * considering the lock to be acquired via fast-path. + */ + locallock->lock = NULL; + locallock->proclock = NULL; + GrantLockLocal(locallock, owner); + return LOCKACQUIRE_OK; + } } + else + pgstat_count_lock_fastpath_exceeded(locallock->tag.lock.locktag_type); } /* diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index fd8318bdf3d..81d20e7ae76 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -1609,9 +1609,15 @@ ProcSleep(LOCALLOCK *locallock) "Processes holding the lock: %s. Wait queue: %s.", lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data)))); else if (myWaitStatus == PROC_WAIT_STATUS_OK) + { + /* Increment the lock statistics counters */ + pgstat_count_lock_waits(locallock->tag.lock.locktag_type); + pgstat_count_lock_wait_time(locallock->tag.lock.locktag_type, msecs); + ereport(LOG, (errmsg("process %d acquired %s on %s after %ld.%03d ms", MyProcPid, modename, buf.data, msecs, usecs))); + } else { Assert(myWaitStatus == PROC_WAIT_STATUS_ERROR); diff --git a/src/backend/utils/activity/Makefile b/src/backend/utils/activity/Makefile index c37bfb350bb..ca3ef89bf59 100644 --- a/src/backend/utils/activity/Makefile +++ b/src/backend/utils/activity/Makefile @@ -26,6 +26,7 @@ OBJS = \ pgstat_database.o \ pgstat_function.o \ pgstat_io.o \ + pgstat_lock.o \ pgstat_relation.o \ pgstat_replslot.o \ pgstat_shmem.o \ diff --git a/src/backend/utils/activity/meson.build b/src/backend/utils/activity/meson.build index 53bd5a246ca..1aa7ece5290 100644 --- a/src/backend/utils/activity/meson.build +++ b/src/backend/utils/activity/meson.build @@ -11,6 +11,7 @@ backend_sources += files( 'pgstat_database.c', 'pgstat_function.c', 'pgstat_io.c', + 'pgstat_lock.c', 'pgstat_relation.c', 'pgstat_replslot.c', 'pgstat_shmem.c', diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index 11bb71cad5a..eb8ccbaa628 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -83,6 +83,7 @@ * - pgstat_database.c * - pgstat_function.c * - pgstat_io.c + * - pgstat_lock.c * - pgstat_relation.c * - pgstat_replslot.c * - pgstat_slru.c @@ -448,6 +449,23 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE] .snapshot_cb = pgstat_io_snapshot_cb, }, + [PGSTAT_KIND_LOCK] = { + .name = "lock", + + .fixed_amount = true, + .write_to_file = true, + + .snapshot_ctl_off = offsetof(PgStat_Snapshot, lock), + .shared_ctl_off = offsetof(PgStat_ShmemControl, lock), + .shared_data_off = offsetof(PgStatShared_Lock, stats), + .shared_data_len = sizeof(((PgStatShared_Lock *) 0)->stats), + + .flush_static_cb = pgstat_lock_flush_cb, + .init_shmem_cb = pgstat_lock_init_shmem_cb, + .reset_all_cb = pgstat_lock_reset_all_cb, + .snapshot_cb = pgstat_lock_snapshot_cb, + }, + [PGSTAT_KIND_SLRU] = { .name = "slru", diff --git a/src/backend/utils/activity/pgstat_lock.c b/src/backend/utils/activity/pgstat_lock.c new file mode 100644 index 00000000000..7af4bc6d018 --- /dev/null +++ b/src/backend/utils/activity/pgstat_lock.c @@ -0,0 +1,162 @@ +/* ------------------------------------------------------------------------- + * + * pgstat_lock.c + * Implementation of lock statistics. + * + * This file contains the implementation of lock statistics. It is kept separate + * from pgstat.c to enforce the line between the statistics access / storage + * implementation and the details about individual types of statistics. + * + * Copyright (c) 2021-2025, PostgreSQL Global Development Group + * + * IDENTIFICATION + * src/backend/utils/activity/pgstat_lock.c + * ------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include "utils/pgstat_internal.h" + +static PgStat_PendingLock PendingLockStats; +static bool have_lockstats = false; + +/* + * Simpler wrapper of pgstat_lock_flush_cb() + */ +void +pgstat_lock_flush(bool nowait) +{ + (void) pgstat_lock_flush_cb(nowait); +} + +/* + * Flush out locally pending lock statistics + * + * If no stats have been recorded, this function returns false. + * + * If nowait is true, this function returns true if the lock could not be + * acquired. Otherwise, return false. + */ +bool +pgstat_lock_flush_cb(bool nowait) +{ + LWLock *lcktype_lock; + PgStat_LockEntry *lck_shstats; + bool lock_not_acquired = false; + + if (!have_lockstats) + return false; + + for (int i = 0; i <= LOCKTAG_LAST_TYPE; i++) + { + lcktype_lock = &pgStatLocal.shmem->lock.locks[i]; + lck_shstats = + &pgStatLocal.shmem->lock.stats.stats[i]; + + if (!nowait) + LWLockAcquire(lcktype_lock, LW_EXCLUSIVE); + else if (!LWLockConditionalAcquire(lcktype_lock, LW_EXCLUSIVE)) + { + lock_not_acquired = true; + continue; + } + +#define LOCKSTAT_ACC(fld) \ + (lck_shstats->fld += PendingLockStats.stats[i].fld) + LOCKSTAT_ACC(waits); + LOCKSTAT_ACC(wait_time); + LOCKSTAT_ACC(fastpath_exceeded); +#undef LOCKSTAT_ACC + + LWLockRelease(lcktype_lock); + } + + memset(&PendingLockStats, 0, sizeof(PendingLockStats)); + + have_lockstats = false; + + return lock_not_acquired; +} + + +void +pgstat_lock_init_shmem_cb(void *stats) +{ + PgStatShared_Lock *stat_shmem = (PgStatShared_Lock *) stats; + + for (int i = 0; i <= LOCKTAG_LAST_TYPE; i++) + LWLockInitialize(&stat_shmem->locks[i], LWTRANCHE_PGSTATS_DATA); +} + +void +pgstat_lock_reset_all_cb(TimestampTz ts) +{ + for (int i = 0; i <= LOCKTAG_LAST_TYPE; i++) + { + LWLock *lcktype_lock = &pgStatLocal.shmem->lock.locks[i]; + PgStat_LockEntry *lck_shstats = &pgStatLocal.shmem->lock.stats.stats[i]; + + LWLockAcquire(lcktype_lock, LW_EXCLUSIVE); + + /* + * Use the lock in the first lock type PgStat_LockEntry to protect the + * reset timestamp as well. + */ + if (i == 0) + pgStatLocal.shmem->lock.stats.stat_reset_timestamp = ts; + + memset(lck_shstats, 0, sizeof(*lck_shstats)); + LWLockRelease(lcktype_lock); + } +} + +void +pgstat_lock_snapshot_cb(void) +{ + for (int i = 0; i <= LOCKTAG_LAST_TYPE; i++) + { + LWLock *lcktype_lock = &pgStatLocal.shmem->lock.locks[i]; + PgStat_LockEntry *lck_shstats = &pgStatLocal.shmem->lock.stats.stats[i]; + PgStat_LockEntry *lck_snap = &pgStatLocal.snapshot.lock.stats[i]; + + LWLockAcquire(lcktype_lock, LW_SHARED); + + /* + * Use the lock in the first lock type PgStat_LockEntry to protect the + * reset timestamp as well. + */ + if (i == 0) + pgStatLocal.snapshot.lock.stat_reset_timestamp = + pgStatLocal.shmem->lock.stats.stat_reset_timestamp; + + /* using struct assignment due to better type safety */ + *lck_snap = *lck_shstats; + LWLockRelease(lcktype_lock); + } +} + +#define PGSTAT_COUNT_LOCK_FUNC(stat) \ +void \ +CppConcat(pgstat_count_lock_,stat)(uint8 locktag_type) \ +{ \ + Assert(locktag_type <= LOCKTAG_LAST_TYPE); \ + PendingLockStats.stats[locktag_type].stat++; \ + have_lockstats = true; \ + pgstat_report_fixed = true; \ +} + +/* pgstat_count_lock_waits */ +PGSTAT_COUNT_LOCK_FUNC(waits) + +/* pgstat_count_lock_fastpath_exceeded */ +PGSTAT_COUNT_LOCK_FUNC(fastpath_exceeded) + +void +pgstat_count_lock_wait_time(uint8 locktag_type, long msecs) +{ + Assert(locktag_type <= LOCKTAG_LAST_TYPE); + PendingLockStats.stats[locktag_type].wait_time += (PgStat_Counter) msecs; + have_lockstats = true; + pgstat_report_fixed = true; +} diff --git a/src/include/pgstat.h b/src/include/pgstat.h index fff7ecc2533..dfbead474b1 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -17,6 +17,7 @@ #include "postmaster/pgarch.h" /* for MAX_XFN_CHARS */ #include "replication/conflict.h" #include "replication/worker_internal.h" +#include "storage/lock.h" #include "utils/backend_progress.h" /* for backward compatibility */ /* IWYU pragma: export */ #include "utils/backend_status.h" /* for backward compatibility */ /* IWYU pragma: export */ #include "utils/pgstat_kind.h" @@ -342,6 +343,24 @@ typedef struct PgStat_IO PgStat_BktypeIO stats[BACKEND_NUM_TYPES]; } PgStat_IO; +typedef struct PgStat_LockEntry +{ + PgStat_Counter waits; + PgStat_Counter wait_time; /* time in milliseconds */ + PgStat_Counter fastpath_exceeded; +} PgStat_LockEntry; + +typedef struct PgStat_PendingLock +{ + PgStat_LockEntry stats[LOCKTAG_LAST_TYPE + 1]; +} PgStat_PendingLock; + +typedef struct PgStat_Lock +{ + TimestampTz stat_reset_timestamp; + PgStat_LockEntry stats[LOCKTAG_LAST_TYPE + 1]; +} PgStat_Lock; + typedef struct PgStat_StatDBEntry { PgStat_Counter xact_commit; @@ -614,6 +633,15 @@ extern bool pgstat_tracks_io_op(BackendType bktype, IOObject io_object, IOContext io_context, IOOp io_op); +/* + * Functions in pgstat_lock.c + */ + +extern void pgstat_lock_flush(bool nowait); +extern void pgstat_count_lock_waits(uint8 locktag_type); +extern void pgstat_count_lock_fastpath_exceeded(uint8 locktag_type); +extern void pgstat_count_lock_wait_time(uint8 locktag_type, long msecs); + /* * Functions in pgstat_database.c */ diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h index 9b8fbae00ed..97704421a92 100644 --- a/src/include/utils/pgstat_internal.h +++ b/src/include/utils/pgstat_internal.h @@ -464,6 +464,16 @@ typedef struct PgStatShared_IO PgStat_IO stats; } PgStatShared_IO; +typedef struct PgStatShared_Lock +{ + /* + * locks[i] protects stats.stats[i]. locks[0] also protects + * stats.stat_reset_timestamp. + */ + LWLock locks[LOCKTAG_LAST_TYPE + 1]; + PgStat_Lock stats; +} PgStatShared_Lock; + typedef struct PgStatShared_SLRU { /* lock protects ->stats */ @@ -570,6 +580,7 @@ typedef struct PgStat_ShmemControl PgStatShared_BgWriter bgwriter; PgStatShared_Checkpointer checkpointer; PgStatShared_IO io; + PgStatShared_Lock lock; PgStatShared_SLRU slru; PgStatShared_Wal wal; @@ -602,6 +613,8 @@ typedef struct PgStat_Snapshot PgStat_IO io; + PgStat_Lock lock; + PgStat_SLRUStats slru[SLRU_NUM_ELEMENTS]; PgStat_WalStats wal; @@ -752,6 +765,14 @@ extern void pgstat_io_init_shmem_cb(void *stats); extern void pgstat_io_reset_all_cb(TimestampTz ts); extern void pgstat_io_snapshot_cb(void); +/* + * Functions in pgstat_lock.c + */ + +extern bool pgstat_lock_flush_cb(bool nowait); +extern void pgstat_lock_init_shmem_cb(void *stats); +extern void pgstat_lock_reset_all_cb(TimestampTz ts); +extern void pgstat_lock_snapshot_cb(void); /* * Functions in pgstat_relation.c diff --git a/src/include/utils/pgstat_kind.h b/src/include/utils/pgstat_kind.h index c30b6235623..2d78a029683 100644 --- a/src/include/utils/pgstat_kind.h +++ b/src/include/utils/pgstat_kind.h @@ -36,8 +36,9 @@ #define PGSTAT_KIND_BGWRITER 8 #define PGSTAT_KIND_CHECKPOINTER 9 #define PGSTAT_KIND_IO 10 -#define PGSTAT_KIND_SLRU 11 -#define PGSTAT_KIND_WAL 12 +#define PGSTAT_KIND_LOCK 11 +#define PGSTAT_KIND_SLRU 12 +#define PGSTAT_KIND_WAL 13 #define PGSTAT_KIND_BUILTIN_MIN PGSTAT_KIND_DATABASE #define PGSTAT_KIND_BUILTIN_MAX PGSTAT_KIND_WAL diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 241945734ec..0432862061b 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2255,6 +2255,7 @@ PgStatShared_Database PgStatShared_Function PgStatShared_HashEntry PgStatShared_IO +PgStatShared_Lock PgStatShared_Relation PgStatShared_ReplSlot PgStatShared_SLRU @@ -2277,8 +2278,11 @@ PgStat_HashKey PgStat_IO PgStat_KindInfo PgStat_LocalState +PgStat_Lock +PgStat_LockEntry PgStat_PendingDroppedStatsItem PgStat_PendingIO +PgStat_PendingLock PgStat_SLRUStats PgStat_ShmemControl PgStat_Snapshot -- 2.34.1