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Wake up autovacuum launcher from postmaster when a worker exits

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When an autovacuum worker exits, the launcher needs to be notified
with SIGUSR2, so that it can rebalance and possibly launch a new
worker. The launcher must be notified only after the worker has
finished ProcKill(), so that the worker slot is available for a new
worker. Before this commit, the autovacuum worker was responsible for
that, which required a slightly complicated dance to pass the
launcher's PID from FreeWorkerInfo() to ProcKill() in a global
variable.

Simplify that by moving the responsibility of the signaling to the
postmaster. The postmaster was already doing it when it failed to fork
a worker process, so it seems logical to make it responsible for
notifying the launcher on worker exit too. That's also how the
notification on background worker exit is done.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: li carol <carol.li2025@outlook.com>
Discussion: https://www.postgresql.org/message-id/a5e27d25-c7e7-45d5-9bac-a17c8f462def@iki.fi
This commit is contained in:
Heikki Linnakangas
2026-01-15 18:02:25 +02:00
parent 102bdaa9be
commit d9c3c94365
4 changed files with 8 additions and 29 deletions
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22
src/backend/postmaster/autovacuum.c
View File

@@ -323,9 +323,6 @@ avl_dbase *avl_dbase_array;
/* Pointer to my own WorkerInfo, valid on each worker */
static WorkerInfo MyWorkerInfo = NULL;
/* PID of launcher, valid only in worker while shutting down */
int AutovacuumLauncherPid = 0;
static Oid do_start_worker(void);
static void ProcessAutoVacLauncherInterrupts(void);
pg_noreturn static void AutoVacLauncherShutdown(void);
@@ -1604,11 +1601,6 @@ AutoVacWorkerMain(const void *startup_data, size_t startup_data_len)
do_autovacuum();
}
/*
* The launcher will be notified of my death in ProcKill, *if* we managed
* to get a worker slot at all
*/
/* All done, go away */
proc_exit(0);
}
@@ -1623,20 +1615,6 @@ FreeWorkerInfo(int code, Datum arg)
{
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
/*
* Wake the launcher up so that he can launch a new worker immediately
* if required. We only save the launcher's PID in local memory here;
* the actual signal will be sent when the PGPROC is recycled. Note
* that we always do this, so that the launcher can rebalance the cost
* limit setting of the remaining workers.
*
* We somewhat ignore the risk that the launcher changes its PID
* between us reading it and the actual kill; we expect ProcKill to be
* called shortly after us, and we assume that PIDs are not reused too
* quickly after a process exits.
*/
AutovacuumLauncherPid = AutoVacuumShmem->av_launcherpid;
dlist_delete(&MyWorkerInfo->wi_links);
MyWorkerInfo->wi_dboid = InvalidOid;
MyWorkerInfo->wi_tableoid = InvalidOid;

8
src/backend/postmaster/postmaster.c
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@@ -2664,6 +2664,14 @@ CleanupBackend(PMChild *bp,
if (bp_bgworker_notify)
BackgroundWorkerStopNotifications(bp_pid);
/*
* If it was an autovacuum worker, wake up the launcher so that it can
* immediately launch a new worker or rebalance to cost limit setting of
* the remaining workers.
*/
if (bp_bkend_type == B_AUTOVAC_WORKER && AutoVacLauncherPMChild != NULL)
signal_child(AutoVacLauncherPMChild, SIGUSR2);
/*
* If it was a background worker, also update its RegisteredBgWorker
* entry.

4
src/backend/storage/lmgr/proc.c
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@@ -1035,10 +1035,6 @@ ProcKill(int code, Datum arg)
ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
SpinLockRelease(ProcStructLock);
/* wake autovac launcher if needed -- see comments in FreeWorkerInfo */
if (AutovacuumLauncherPid != 0)
kill(AutovacuumLauncherPid, SIGUSR2);
}
/*

3
src/include/postmaster/autovacuum.h
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@@ -44,9 +44,6 @@ extern PGDLLIMPORT int autovacuum_multixact_freeze_max_age;
extern PGDLLIMPORT double autovacuum_vac_cost_delay;
extern PGDLLIMPORT int autovacuum_vac_cost_limit;
/* autovacuum launcher PID, only valid when worker is shutting down */
extern PGDLLIMPORT int AutovacuumLauncherPid;
extern PGDLLIMPORT int Log_autovacuum_min_duration;
extern PGDLLIMPORT int Log_autoanalyze_min_duration;