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 <[email protected]> (parts)
Tested-by: Jakub Wartak <[email protected]>
Discussion: https://postgr.es/m/CA+hUKGLJ=84YT+NvhkEEDAuUtVHMfQ9i-N7k_o50JmQ6Rpj_OQ@mail.gmail.com

5 files changed, 25 insertions, 6 deletions

diff --git a/src/include/access/clog.h b/src/include/access/clog.h
index 2db8acb189f..6c840cbf299 100644
--- a/src/include/access/clog.h
+++ b/src/include/access/clog.h
@@ -12,6 +12,7 @@
 #define CLOG_H
 
 #include "access/xlogreader.h"
+#include "storage/sync.h"
 #include "lib/stringinfo.h"
 
 /*
@@ -50,6 +51,8 @@ extern void CheckPointCLOG(void);
 extern void ExtendCLOG(TransactionId newestXact);
 extern void TruncateCLOG(TransactionId oldestXact, Oid oldestxid_datoid);
 
+extern int	clogsyncfiletag(const FileTag *ftag, char *path);
+
 /* XLOG stuff */
 #define CLOG_ZEROPAGE		0x00
 #define CLOG_TRUNCATE		0x10
diff --git a/src/include/access/commit_ts.h b/src/include/access/commit_ts.h
index 2740c02a84f..2d172495225 100644
--- a/src/include/access/commit_ts.h
+++ b/src/include/access/commit_ts.h
@@ -14,6 +14,7 @@
 #include "access/xlog.h"
 #include "datatype/timestamp.h"
 #include "replication/origin.h"
+#include "storage/sync.h"
 #include "utils/guc.h"
 
 
@@ -45,6 +46,8 @@ extern void SetCommitTsLimit(TransactionId oldestXact,
 							 TransactionId newestXact);
 extern void AdvanceOldestCommitTsXid(TransactionId oldestXact);
 
+extern int	committssyncfiletag(const FileTag *ftag, char *path);
+
 /* XLOG stuff */
 #define COMMIT_TS_ZEROPAGE		0x00
 #define COMMIT_TS_TRUNCATE		0x10
diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h
index 6d729008c60..58c42ffe1fe 100644
--- a/src/include/access/multixact.h
+++ b/src/include/access/multixact.h
@@ -13,6 +13,7 @@
 
 #include "access/xlogreader.h"
 #include "lib/stringinfo.h"
+#include "storage/sync.h"
 
 
 /*
@@ -116,6 +117,9 @@ extern bool MultiXactIdPrecedes(MultiXactId multi1, MultiXactId multi2);
 extern bool MultiXactIdPrecedesOrEquals(MultiXactId multi1,
 										MultiXactId multi2);
 
+extern int	multixactoffsetssyncfiletag(const FileTag *ftag, char *path);
+extern int	multixactmemberssyncfiletag(const FileTag *ftag, char *path);
+
 extern void AtEOXact_MultiXact(void);
 extern void AtPrepare_MultiXact(void);
 extern void PostPrepare_MultiXact(TransactionId xid);
diff --git a/src/include/access/slru.h b/src/include/access/slru.h
index 61fbc80ef0d..b39b43504d8 100644
--- a/src/include/access/slru.h
+++ b/src/include/access/slru.h
@@ -15,6 +15,7 @@
 
 #include "access/xlogdefs.h"
 #include "storage/lwlock.h"
+#include "storage/sync.h"
 
 
 /*
@@ -111,10 +112,10 @@ typedef struct SlruCtlData
 	SlruShared	shared;
 
 	/*
-	 * This flag tells whether to fsync writes (true for pg_xact and multixact
-	 * stuff, false for pg_subtrans and pg_notify).
+	 * Which sync handler function to use when handing sync requests over to
+	 * the checkpointer.  SYNC_HANDLER_NONE to disable fsync (eg pg_notify).
 	 */
-	bool		do_fsync;
+	SyncRequestHandler sync_handler;
 
 	/*
 	 * Decide which of two page numbers is "older" for truncation purposes. We
@@ -135,14 +136,15 @@ typedef SlruCtlData *SlruCtl;
 
 extern Size SimpleLruShmemSize(int nslots, int nlsns);
 extern void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
-						  LWLock *ctllock, const char *subdir, int tranche_id);
+						  LWLock *ctllock, const char *subdir, int tranche_id,
+						  SyncRequestHandler sync_handler);
 extern int	SimpleLruZeroPage(SlruCtl ctl, int pageno);
 extern int	SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
 							  TransactionId xid);
 extern int	SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno,
 									   TransactionId xid);
 extern void SimpleLruWritePage(SlruCtl ctl, int slotno);
-extern void SimpleLruFlush(SlruCtl ctl, bool allow_redirtied);
+extern void SimpleLruWriteAll(SlruCtl ctl, bool allow_redirtied);
 extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
 extern bool SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno);
 
@@ -151,6 +153,8 @@ typedef bool (*SlruScanCallback) (SlruCtl ctl, char *filename, int segpage,
 extern bool SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data);
 extern void SlruDeleteSegment(SlruCtl ctl, int segno);
 
+extern int	SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path);
+
 /* SlruScanDirectory public callbacks */
 extern bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename,
 										int segpage, void *data);
diff --git a/src/include/storage/sync.h b/src/include/storage/sync.h
index e16ab8e711c..f32e412e751 100644
--- a/src/include/storage/sync.h
+++ b/src/include/storage/sync.h
@@ -34,7 +34,12 @@ typedef enum SyncRequestType
  */
 typedef enum SyncRequestHandler
 {
-	SYNC_HANDLER_MD = 0			/* md smgr */
+	SYNC_HANDLER_MD = 0,
+	SYNC_HANDLER_CLOG,
+	SYNC_HANDLER_COMMIT_TS,
+	SYNC_HANDLER_MULTIXACT_OFFSET,
+	SYNC_HANDLER_MULTIXACT_MEMBER,
+	SYNC_HANDLER_NONE
 } SyncRequestHandler;
 
 /*