postgres.git / summary / log / commit / refs

commit    2bef57ee8b38ee7fdbad3fb38b1f8ed31adb381b
Author:   Thomas Munro <tmunro@postgresql.org>
Date:     Wed Mar 15 00:57:00 2023 +0000

    Fix fractional vacuum_cost_delay.
    
    Commit 4753ef37 changed vacuum_delay_point() to use the WaitLatch() API,
    to fix the problem that vacuum could keep running for a very long time
    after the postmaster died.
    
    Unfortunately, that broke commit caf626b2's support for fractional
    vacuum_cost_delay, which shipped in PostgreSQL 12.  WaitLatch() works in
    whole milliseconds.
    
    For now, revert the change from commit 4753ef37, but add an explicit
    check for postmaster death.  That's an extra system call on systems
    other than Linux and FreeBSD, but that overhead doesn't matter much
    considering that we willingly went to sleep and woke up again.  (In
    later work, we might add higher resolution timeouts to the latch API so
    that we could do this with our standard programming pattern, but that
    wouldn't be back-patched.)
    
    Back-patch to 14, where commit 4753ef37 arrived.
    
    Reported-by: Melanie Plageman <melanieplageman@gmail.com>
    Discussion: https://postgr.es/m/CAAKRu_b-q0hXCBUCAATh0Z4Zi6UkiC0k2DFgoD3nC-r3SkR3tg%40mail.gmail.com


 src/backend/commands/vacuum.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 5c4bc15b441..ac69b4dc231 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -45,6 +45,7 @@
 #include "postmaster/bgworker_internals.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
+#include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
@@ -2171,11 +2172,18 @@ vacuum_delay_point(void)
 		if (msec > VacuumCostDelay * 4)
 			msec = VacuumCostDelay * 4;
 
-		(void) WaitLatch(MyLatch,
-						 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
-						 msec,
-						 WAIT_EVENT_VACUUM_DELAY);
-		ResetLatch(MyLatch);
+		pgstat_report_wait_start(WAIT_EVENT_VACUUM_DELAY);
+		pg_usleep(msec * 1000);
+		pgstat_report_wait_end();
+
+		/*
+		 * We don't want to ignore postmaster death during very long vacuums
+		 * with vacuum_cost_delay configured.  We can't use the usual
+		 * WaitLatch() approach here because we want microsecond-based sleep
+		 * durations above.
+		 */
+		if (IsUnderPostmaster && !PostmasterIsAlive())
+			exit(1);
 
 		VacuumCostBalance = 0;
 


[parent: 9b6e0b9c37d6]