Add wait events for checkpoint delay mechanism.

macdice · macdice · commit 0013ba290b66 · 2023-10-13T16:43:22.000+13:00
When MyProc->delayChkptFlags is set to temporarily block phase transitions in a concurrent checkpoint, the checkpointer enters a sleep-poll loop to wait for the flag to be cleared. We should show that as a wait event in the pg_stat_activity view. Reviewed-by: Robert Haas <robertmhaas@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/CA%2BhUKGL7Whi8iwKbzkbn_1fixH3Yy8aAPz7mfq6Hpj7FeJrKMg%40mail.gmail.com
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
@@ -6737,7 +6737,9 @@ CreateCheckPoint(int flags)
 	{
 		do
 		{
+			pgstat_report_wait_start(WAIT_EVENT_CHECKPOINT_DELAY_START);
 			pg_usleep(10000L);	/* wait for 10 msec */
+			pgstat_report_wait_end();
 		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
 											  DELAY_CHKPT_START));
 	}
@@ -6750,7 +6752,9 @@ CreateCheckPoint(int flags)
 	{
 		do
 		{
+			pgstat_report_wait_start(WAIT_EVENT_CHECKPOINT_DELAY_COMPLETE);
 			pg_usleep(10000L);	/* wait for 10 msec */
+			pgstat_report_wait_end();
 		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
 											  DELAY_CHKPT_COMPLETE));
 	}
diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt
@@ -97,6 +97,8 @@ BGWORKER_SHUTDOWN	"Waiting for background worker to shut down."
 BGWORKER_STARTUP	"Waiting for background worker to start up."
 BTREE_PAGE	"Waiting for the page number needed to continue a parallel B-tree scan to become available."
 BUFFER_IO	"Waiting for buffer I/O to complete."
+CHECKPOINT_DELAY_COMPLETE	"Waiting for a backend that blocks a checkpoint from completing."
+CHECKPOINT_DELAY_START	"Waiting for a backend that blocks a checkpoint from starting."
 CHECKPOINT_DONE	"Waiting for a checkpoint to complete."
 CHECKPOINT_START	"Waiting for a checkpoint to start."
 EXECUTE_GATHER	"Waiting for activity from a child process while executing a <literal>Gather</literal> plan node."

Original file line number	Diff line number	Diff line change
`@@ -6737,7 +6737,9 @@ CreateCheckPoint(int flags)`
`6737`	`6737`	`{`
`6738`	`6738`	`do`
`6739`	`6739`	`{`
	`6740`	`+ pgstat_report_wait_start(WAIT_EVENT_CHECKPOINT_DELAY_START);`
`6740`	`6741`	`pg_usleep(10000L); /* wait for 10 msec */`
	`6742`	`+ pgstat_report_wait_end();`
`6741`	`6743`	`} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,`
`6742`	`6744`	`DELAY_CHKPT_START));`
`6743`	`6745`	`}`
`@@ -6750,7 +6752,9 @@ CreateCheckPoint(int flags)`
`6750`	`6752`	`{`
`6751`	`6753`	`do`
`6752`	`6754`	`{`
	`6755`	`+ pgstat_report_wait_start(WAIT_EVENT_CHECKPOINT_DELAY_COMPLETE);`
`6753`	`6756`	`pg_usleep(10000L); /* wait for 10 msec */`
	`6757`	`+ pgstat_report_wait_end();`
`6754`	`6758`	`} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,`
`6755`	`6759`	`DELAY_CHKPT_COMPLETE));`
`6756`	`6760`	`}`