From 1396b5c6ed2bf46433c77ad0ce7f1ddaa984c224 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Wed, 16 Mar 2022 15:35:42 +1300 Subject: [PATCH] Fix waiting in RegisterSyncRequest(). If we run out of space in the checkpointer sync request queue (which is hopefully rare on real systems, but common with very small buffer pool), we wait for it to drain. While waiting, we should report that as a wait event so that users know what is going on, and also handle postmaster death, since otherwise the loop might never terminate if the checkpointer has exited. Back-patch to 12. Although the problem exists in earlier releases too, the code is structured differently before 12 so I haven't gone any further for now, in the absence of field complaints. Reported-by: Andres Freund Reviewed-by: Andres Freund Discussion: https://postgr.es/m/20220226213942.nb7uvb2pamyu26dj%40alap3.anarazel.de --- doc/src/sgml/monitoring.sgml | 5 +++++ src/backend/storage/sync/sync.c | 4 +++- src/backend/utils/activity/wait_event.c | 3 +++ src/include/utils/wait_event.h | 3 ++- 4 files changed, 13 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index b8ffc210a4a..cfddd33da1d 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -2242,6 +2242,11 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser Waiting during recovery when WAL data is not available from any source (pg_wal, archive or stream). + + RegisterSyncRequest + Waiting while sending synchronization requests to the + checkpointer, because the request queue is full. + VacuumDelay Waiting in a cost-based vacuum delay point. diff --git a/src/backend/storage/sync/sync.c b/src/backend/storage/sync/sync.c index a12b3572759..ea076a4106a 100644 --- a/src/backend/storage/sync/sync.c +++ b/src/backend/storage/sync/sync.c @@ -30,6 +30,7 @@ #include "postmaster/bgwriter.h" #include "storage/bufmgr.h" #include "storage/ipc.h" +#include "storage/latch.h" #include "storage/md.h" #include "utils/hsearch.h" #include "utils/inval.h" @@ -606,7 +607,8 @@ RegisterSyncRequest(const FileTag *ftag, SyncRequestType type, if (ret || (!ret && !retryOnError)) break; - pg_usleep(10000L); + WaitLatch(NULL, WL_EXIT_ON_PM_DEATH | WL_TIMEOUT, 10, + WAIT_EVENT_REGISTER_SYNC_REQUEST); } return ret; diff --git a/src/backend/utils/activity/wait_event.c b/src/backend/utils/activity/wait_event.c index affbcf25db6..1a30faf8ad4 100644 --- a/src/backend/utils/activity/wait_event.c +++ b/src/backend/utils/activity/wait_event.c @@ -485,6 +485,9 @@ pgstat_get_wait_timeout(WaitEventTimeout w) case WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL: event_name = "RecoveryRetrieveRetryInterval"; break; + case WAIT_EVENT_REGISTER_SYNC_REQUEST: + event_name = "RegisterSyncRequest"; + break; case WAIT_EVENT_VACUUM_DELAY: event_name = "VacuumDelay"; break; diff --git a/src/include/utils/wait_event.h b/src/include/utils/wait_event.h index 1fb6f640138..4b1cea65938 100644 --- a/src/include/utils/wait_event.h +++ b/src/include/utils/wait_event.h @@ -141,7 +141,8 @@ typedef enum WAIT_EVENT_RECOVERY_APPLY_DELAY, WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL, WAIT_EVENT_VACUUM_DELAY, - WAIT_EVENT_CHECKPOINT_WRITE_DELAY + WAIT_EVENT_CHECKPOINT_WRITE_DELAY, + WAIT_EVENT_REGISTER_SYNC_REQUEST } WaitEventTimeout; /* ----------