From dee663f7843902535a15ae366cede8b4089f1144 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Fri, 25 Sep 2020 18:49:43 +1200 Subject: Defer flushing of SLRU files. Previously, we called fsync() after writing out individual pg_xact, pg_multixact and pg_commit_ts pages due to cache pressure, leading to regular I/O stalls in user backends and recovery. Collapse requests for the same file into a single system call as part of the next checkpoint, as we already did for relation files, using the infrastructure developed by commit 3eb77eba. This can cause a significant improvement to recovery performance, especially when it's otherwise CPU-bound. Hoist ProcessSyncRequests() up into CheckPointGuts() to make it clearer that it applies to all the SLRU mini-buffer-pools as well as the main buffer pool. Rearrange things so that data collected in CheckpointStats includes SLRU activity. Also remove the Shutdown{CLOG,CommitTS,SUBTRANS,MultiXact}() functions, because they were redundant after the shutdown checkpoint that immediately precedes them. (I'm not sure if they were ever needed, but they aren't now.) Reviewed-by: Tom Lane (parts) Tested-by: Jakub Wartak Discussion: https://postgr.es/m/CA+hUKGLJ=84YT+NvhkEEDAuUtVHMfQ9i-N7k_o50JmQ6Rpj_OQ@mail.gmail.com --- src/backend/access/transam/xlog.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'src/backend/access/transam/xlog.c') diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 61754312e26..79a77ebbfe2 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -8528,10 +8528,6 @@ ShutdownXLOG(int code, Datum arg) CreateCheckPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE); } - ShutdownCLOG(); - ShutdownCommitTs(); - ShutdownSUBTRANS(); - ShutdownMultiXact(); } /* @@ -9176,17 +9172,29 @@ CreateEndOfRecoveryRecord(void) static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags) { - CheckPointCLOG(); - CheckPointCommitTs(); - CheckPointSUBTRANS(); - CheckPointMultiXact(); - CheckPointPredicate(); CheckPointRelationMap(); CheckPointReplicationSlots(); CheckPointSnapBuild(); CheckPointLogicalRewriteHeap(); - CheckPointBuffers(flags); /* performs all required fsyncs */ CheckPointReplicationOrigin(); + + /* Write out all dirty data in SLRUs and the main buffer pool */ + TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags); + CheckpointStats.ckpt_write_t = GetCurrentTimestamp(); + CheckPointCLOG(); + CheckPointCommitTs(); + CheckPointSUBTRANS(); + CheckPointMultiXact(); + CheckPointPredicate(); + CheckPointBuffers(flags); + + /* Perform all queued up fsyncs */ + TRACE_POSTGRESQL_BUFFER_CHECKPOINT_SYNC_START(); + CheckpointStats.ckpt_sync_t = GetCurrentTimestamp(); + ProcessSyncRequests(); + CheckpointStats.ckpt_sync_end_t = GetCurrentTimestamp(); + TRACE_POSTGRESQL_BUFFER_CHECKPOINT_DONE(); + /* We deliberately delay 2PC checkpointing as long as possible */ CheckPointTwoPhase(checkPointRedo); } -- cgit v1.2.3