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Defer flushing of SLRU files.

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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 <tgl@sss.pgh.pa.us> (parts)
Tested-by: Jakub Wartak <Jakub.Wartak@tomtom.com>
Discussion: https://postgr.es/m/CA+hUKGLJ=84YT+NvhkEEDAuUtVHMfQ9i-N7k_o50JmQ6Rpj_OQ@mail.gmail.com
This commit is contained in:
Thomas Munro
2020-09-25 18:49:43 +12:00
parent ca7f8e2b86
commit dee663f784
16 changed files with 255 additions and 175 deletions
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40
src/backend/access/transam/clog.c
View File

@ -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);
}