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/clog.c | 40 ++++++++++++++++++--------------------- 1 file changed, 18 insertions(+), 22 deletions(-) (limited to 'src/backend/access/transam/clog.c') diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c index 9e352d26583..034349aa7b9 100644 --- a/src/backend/access/transam/clog.c +++ b/src/backend/access/transam/clog.c @@ -42,6 +42,7 @@ #include "pg_trace.h" #include "pgstat.h" #include "storage/proc.h" +#include "storage/sync.h" /* * Defines for CLOG page sizes. A page is the same BLCKSZ as is used @@ -691,7 +692,8 @@ CLOGShmemInit(void) { XactCtl->PagePrecedes = CLOGPagePrecedes; SimpleLruInit(XactCtl, "Xact", CLOGShmemBuffers(), CLOG_LSNS_PER_PAGE, - XactSLRULock, "pg_xact", LWTRANCHE_XACT_BUFFER); + XactSLRULock, "pg_xact", LWTRANCHE_XACT_BUFFER, + SYNC_HANDLER_CLOG); } /* @@ -808,34 +810,19 @@ TrimCLOG(void) LWLockRelease(XactSLRULock); } -/* - * This must be called ONCE during postmaster or standalone-backend shutdown - */ -void -ShutdownCLOG(void) -{ - /* Flush dirty CLOG pages to disk */ - TRACE_POSTGRESQL_CLOG_CHECKPOINT_START(false); - SimpleLruFlush(XactCtl, false); - - /* - * fsync pg_xact to ensure that any files flushed previously are durably - * on disk. - */ - fsync_fname("pg_xact", true); - - TRACE_POSTGRESQL_CLOG_CHECKPOINT_DONE(false); -} - /* * Perform a checkpoint --- either during shutdown, or on-the-fly */ void CheckPointCLOG(void) { - /* Flush dirty CLOG pages to disk */ + /* + * Write dirty CLOG pages to disk. This may result in sync requests + * queued for later handling by ProcessSyncRequests(), as part of the + * checkpoint. + */ TRACE_POSTGRESQL_CLOG_CHECKPOINT_START(true); - SimpleLruFlush(XactCtl, true); + SimpleLruWriteAll(XactCtl, true); TRACE_POSTGRESQL_CLOG_CHECKPOINT_DONE(true); } @@ -1026,3 +1013,12 @@ clog_redo(XLogReaderState *record) else elog(PANIC, "clog_redo: unknown op code %u", info); } + +/* + * Entrypoint for sync.c to sync clog files. + */ +int +clogsyncfiletag(const FileTag *ftag, char *path) +{ + return SlruSyncFileTag(XactCtl, ftag, path); +} -- cgit v1.2.3