From 9dcf4a45b6ed7d8fca1a1cd6782f11dff3a84406 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Mon, 17 Jul 2023 09:20:05 -0700 Subject: [PATCH v1] Caller specified wait events for LWLockWaitForVar(), LWLockAcquireOrWait() Reporting waits within those functions as LWLock wait events is misleading, as we do not actually wait for the lock themselves. Author: Reviewed-by: Discussion: https://postgr.es/m/ Backpatch: --- src/include/storage/lwlock.h | 6 ++++-- src/backend/access/transam/xlog.c | 6 ++++-- src/backend/storage/lmgr/lwlock.c | 19 +++++++++++++------ .../utils/activity/wait_event_names.txt | 2 ++ 4 files changed, 23 insertions(+), 10 deletions(-) diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h index 34169e5889e..0f345076f41 100644 --- a/src/include/storage/lwlock.h +++ b/src/include/storage/lwlock.h @@ -127,7 +127,8 @@ extern PGDLLIMPORT bool Trace_lwlocks; extern bool LWLockAcquire(LWLock *lock, LWLockMode mode); extern bool LWLockConditionalAcquire(LWLock *lock, LWLockMode mode); -extern bool LWLockAcquireOrWait(LWLock *lock, LWLockMode mode); +extern bool LWLockAcquireOrWait(LWLock *lock, LWLockMode mode, + uint32 wait_event_info); extern void LWLockRelease(LWLock *lock); extern void LWLockReleaseClearVar(LWLock *lock, uint64 *valptr, uint64 val); extern void LWLockReleaseAll(void); @@ -135,7 +136,8 @@ extern bool LWLockHeldByMe(LWLock *lock); extern bool LWLockAnyHeldByMe(LWLock *lock, int nlocks, size_t stride); extern bool LWLockHeldByMeInMode(LWLock *lock, LWLockMode mode); -extern bool LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval); +extern bool LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, + uint32 wait_event_info); extern void LWLockUpdateVar(LWLock *lock, uint64 *valptr, uint64 val); extern Size LWLockShmemSize(void); diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 8b0710abe60..e406634c1cf 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1498,7 +1498,8 @@ WaitXLogInsertionsToFinish(XLogRecPtr upto) */ if (LWLockWaitForVar(&WALInsertLocks[i].l.lock, &WALInsertLocks[i].l.insertingAt, - insertingat, &insertingat)) + insertingat, &insertingat, + WAIT_EVENT_WAL_WAIT_INSERT)) { /* the lock was free, so no insertion in progress */ insertingat = InvalidXLogRecPtr; @@ -2586,7 +2587,8 @@ XLogFlush(XLogRecPtr record) * helps to maintain a good rate of group committing when the system * is bottlenecked by the speed of fsyncing. */ - if (!LWLockAcquireOrWait(WALWriteLock, LW_EXCLUSIVE)) + if (!LWLockAcquireOrWait(WALWriteLock, LW_EXCLUSIVE, + WAIT_EVENT_WAL_WAIT_WRITE)) { /* * The lock is now free, but we didn't acquire it yet. Before we diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c index 01d738f306b..549b061b533 100644 --- a/src/backend/storage/lmgr/lwlock.c +++ b/src/backend/storage/lmgr/lwlock.c @@ -1418,9 +1418,12 @@ LWLockConditionalAcquire(LWLock *lock, LWLockMode mode) * backends as a side-effect. Those other backends need to wait until the * flush finishes, but don't need to acquire the lock anymore. They can just * wake up, observe that their records have already been flushed, and return. + * + * As this is not used to *wait* for lwlock acquisition, the caller has to + * provide a wait event to be reported. */ bool -LWLockAcquireOrWait(LWLock *lock, LWLockMode mode) +LWLockAcquireOrWait(LWLock *lock, LWLockMode mode, uint32 wait_event_info) { PGPROC *proc = MyProc; bool mustwait; @@ -1470,7 +1473,7 @@ LWLockAcquireOrWait(LWLock *lock, LWLockMode mode) lwstats->block_count++; #endif - LWLockReportWaitStart(lock); + pgstat_report_wait_start(wait_event_info); if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED()) TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode); @@ -1492,7 +1495,7 @@ LWLockAcquireOrWait(LWLock *lock, LWLockMode mode) #endif if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED()) TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode); - LWLockReportWaitEnd(); + pgstat_report_wait_end(); LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened"); } @@ -1605,9 +1608,13 @@ LWLockConflictsWithVar(LWLock *lock, * * Note: this function ignores shared lock holders; if the lock is held * in shared mode, returns 'true'. + * + * As this is not used to wait for lwlocks themselves, the caller has to + * provide a wait event to be reported. */ bool -LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval) +LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, + uint32 wait_event_info) { PGPROC *proc = MyProc; int extraWaits = 0; @@ -1686,7 +1693,7 @@ LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval) lwstats->block_count++; #endif - LWLockReportWaitStart(lock); + pgstat_report_wait_start(wait_event_info); if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED()) TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE); @@ -1709,7 +1716,7 @@ LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval) if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED()) TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE); - LWLockReportWaitEnd(); + pgstat_report_wait_end(); LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened"); diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt index 3fabad96d96..a9358538721 100644 --- a/src/backend/utils/activity/wait_event_names.txt +++ b/src/backend/utils/activity/wait_event_names.txt @@ -141,6 +141,8 @@ WAIT_EVENT_SYNC_REP SyncRep "Waiting for confirmation from a remote server durin WAIT_EVENT_WAL_RECEIVER_EXIT WalReceiverExit "Waiting for the WAL receiver to exit." WAIT_EVENT_WAL_RECEIVER_WAIT_START WalReceiverWaitStart "Waiting for startup process to send initial data for streaming replication." WAIT_EVENT_XACT_GROUP_UPDATE XactGroupUpdate "Waiting for the group leader to update transaction status at end of a parallel operation." +WAIT_EVENT_WAL_WAIT_INSERT WALWaitInsert "Waiting for WAL record to be copied into buffers." +WAIT_EVENT_WAL_WAIT_WRITE WALWaitWrite "Waiting for WAL buffers to be written or flushed to disk." # -- 2.38.0