Add wait event for fsync of WAL segments

michaelpq · michaelpq · commit c55de5e5123c · 2018-07-02T22:19:46.000+09:00
This has been visibly a forgotten spot in the first implementation of wait events for I/O added by 249cf07, and what has been missing is a fsync call for WAL segments which is a wrapper reacting on the value of GUC wal_sync_method. Reported-by: Konstantin Knizhnik Author: Konstantin Knizhnik Reviewed-by: Craig Ringer, Michael Paquier Discussion: https://postgr.es/m/4a243897-0ad8-f471-aa40-242591f2476e@postgrespro.ru
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
@@ -1674,6 +1674,10 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
          <entry><literal>WALSenderTimelineHistoryRead</literal></entry>
          <entry>Waiting for a read from a timeline history file during walsender timeline command.</entry>
         </row>
+        <row>
+         <entry><literal>WALSync</literal></entry>
+         <entry>Waiting for a WAL file to reach stable storage.</entry>
+        </row>
         <row>
          <entry><literal>WALSyncMethodAssign</literal></entry>
          <entry>Waiting for data to reach stable storage while assigning WAL sync method.</entry>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -10156,6 +10156,7 @@ assign_xlog_sync_method(int new_sync_method, void *extra)
 void
 issue_xlog_fsync(int fd, XLogSegNo segno)
 {
+	pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);
 	switch (sync_method)
 	{
 		case SYNC_METHOD_FSYNC:
@@ -10191,6 +10192,7 @@ issue_xlog_fsync(int fd, XLogSegNo segno)
 			elog(PANIC, "unrecognized wal_sync_method: %d", sync_method);
 			break;
 	}
+	pgstat_report_wait_end();
 }
 
 /*
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
@@ -3925,6 +3925,9 @@ pgstat_get_wait_io(WaitEventIO w)
 		case WAIT_EVENT_WAL_READ:
 			event_name = "WALRead";
 			break;
+		case WAIT_EVENT_WAL_SYNC:
+			event_name = "WALSync";
+			break;
 		case WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN:
 			event_name = "WALSyncMethodAssign";
 			break;
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
@@ -921,6 +921,7 @@ typedef enum
 	WAIT_EVENT_WAL_INIT_SYNC,
 	WAIT_EVENT_WAL_INIT_WRITE,
 	WAIT_EVENT_WAL_READ,
+	WAIT_EVENT_WAL_SYNC,
 	WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN,
 	WAIT_EVENT_WAL_WRITE
 } WaitEventIO;

Original file line number	Diff line number	Diff line change
`@@ -10156,6 +10156,7 @@ assign_xlog_sync_method(int new_sync_method, void *extra)`
`10156`	`10156`	`void`
`10157`	`10157`	`issue_xlog_fsync(int fd, XLogSegNo segno)`
`10158`	`10158`	`{`
	`10159`	`+ pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);`
`10159`	`10160`	`switch (sync_method)`
`10160`	`10161`	`{`
`10161`	`10162`	`case SYNC_METHOD_FSYNC:`
`@@ -10191,6 +10192,7 @@ issue_xlog_fsync(int fd, XLogSegNo segno)`
`10191`	`10192`	`elog(PANIC, "unrecognized wal_sync_method: %d", sync_method);`
`10192`	`10193`	`break;`
`10193`	`10194`	`}`
	`10195`	`+ pgstat_report_wait_end();`
`10194`	`10196`	`}`
`10195`	`10197`
`10196`	`10198`	`/*`