On Fri, Jun 21, 2024 at 03:44:07PM -0500, Nathan Bossart wrote:
> I'm still not sure about this approach. At the moment, I'm leaning towards
> something more like v2 [2] where the upper limit is a PGC_POSTMASTER GUC
> (that we would set very low for TAP tests).
Like so.
--
nathan
>From c1c33c6c157a7cec81180714369b2978b09e402f Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nat...@postgresql.org>
Date: Sat, 22 Jun 2024 15:05:44 -0500
Subject: [PATCH v6 1/1] allow changing autovacuum_max_workers without
restarting
---
doc/src/sgml/config.sgml | 28 +++++++++++-
doc/src/sgml/runtime.sgml | 12 ++---
src/backend/access/transam/xlog.c | 2 +-
src/backend/postmaster/autovacuum.c | 44 ++++++++++++-------
src/backend/postmaster/postmaster.c | 2 +-
src/backend/storage/lmgr/proc.c | 6 +--
src/backend/utils/init/postinit.c | 12 ++---
src/backend/utils/misc/guc_tables.c | 13 +++++-
src/backend/utils/misc/postgresql.conf.sample | 3 +-
src/include/postmaster/autovacuum.h | 1 +
src/include/utils/guc_hooks.h | 4 +-
src/test/perl/PostgreSQL/Test/Cluster.pm | 1 +
12 files changed, 89 insertions(+), 39 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0c7a9082c5..64411918a4 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -8544,6 +8544,25 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH
csv;
</listitem>
</varlistentry>
+ <varlistentry id="guc-autovacuum-worker-slots"
xreflabel="autovacuum_worker_slots">
+ <term><varname>autovacuum_worker_slots</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>autovacuum_worker_slots</varname> configuration
parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Specifies the number of backend slots to reserve for autovacuum worker
+ processes. The default is 16. This parameter can only be set at
server
+ start.
+ </para>
+ <para>
+ When changing this value, consider also adjusting
+ <xref linkend="guc-autovacuum-max-workers"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-autovacuum-max-workers"
xreflabel="autovacuum_max_workers">
<term><varname>autovacuum_max_workers</varname> (<type>integer</type>)
<indexterm>
@@ -8554,7 +8573,14 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH
csv;
<para>
Specifies the maximum number of autovacuum processes (other than the
autovacuum launcher) that may be running at any one time. The default
- is three. This parameter can only be set at server start.
+ is three. This parameter can only be set in the
+ <filename>postgresql.conf</filename> file or on the server command
line.
+ </para>
+ <para>
+ Note that a setting for this value which is higher than
+ <xref linkend="guc-autovacuum-worker-slots"/> will have no effect,
+ since autovacuum workers are taken from the pool of slots established
+ by that setting.
</para>
</listitem>
</varlistentry>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 2f7c618886..4bb37faffe 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -781,13 +781,13 @@ psql: error: connection to server on socket
"/tmp/.s.PGSQL.5432" failed: No such
<row>
<entry><varname>SEMMNI</varname></entry>
<entry>Maximum number of semaphore identifiers (i.e., sets)</entry>
- <entry>at least <literal>ceil((max_connections +
autovacuum_max_workers + max_wal_senders + max_worker_processes + 7) /
16)</literal> plus room for other applications</entry>
+ <entry>at least <literal>ceil((max_connections +
autovacuum_worker_slots + max_wal_senders + max_worker_processes + 7) /
16)</literal> plus room for other applications</entry>
</row>
<row>
<entry><varname>SEMMNS</varname></entry>
<entry>Maximum number of semaphores system-wide</entry>
- <entry><literal>ceil((max_connections + autovacuum_max_workers +
max_wal_senders + max_worker_processes + 7) / 16) * 17</literal> plus room for
other applications</entry>
+ <entry><literal>ceil((max_connections + autovacuum_worker_slots +
max_wal_senders + max_worker_processes + 7) / 16) * 17</literal> plus room for
other applications</entry>
</row>
<row>
@@ -838,7 +838,7 @@ psql: error: connection to server on socket
"/tmp/.s.PGSQL.5432" failed: No such
When using System V semaphores,
<productname>PostgreSQL</productname> uses one semaphore per allowed
connection
(<xref linkend="guc-max-connections"/>), allowed autovacuum worker process
- (<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL sender process
+ (<xref linkend="guc-autovacuum-worker-slots"/>), allowed WAL sender process
(<xref linkend="guc-max-wal-senders"/>), and allowed background
process (<xref linkend="guc-max-worker-processes"/>), in sets of 16.
Each such set will
@@ -847,13 +847,13 @@ psql: error: connection to server on socket
"/tmp/.s.PGSQL.5432" failed: No such
other applications. The maximum number of semaphores in the system
is set by <varname>SEMMNS</varname>, which consequently must be at least
as high as <varname>max_connections</varname> plus
- <varname>autovacuum_max_workers</varname> plus
<varname>max_wal_senders</varname>,
+ <varname>autovacuum_worker_slots</varname> plus
<varname>max_wal_senders</varname>,
plus <varname>max_worker_processes</varname>, plus one extra for each 16
allowed connections plus workers (see the formula in <xref
linkend="sysvipc-parameters"/>). The parameter <varname>SEMMNI</varname>
determines the limit on the number of semaphore sets that can
exist on the system at one time. Hence this parameter must be at
- least <literal>ceil((max_connections + autovacuum_max_workers +
max_wal_senders + max_worker_processes + 7) / 16)</literal>.
+ least <literal>ceil((max_connections + autovacuum_worker_slots +
max_wal_senders + max_worker_processes + 7) / 16)</literal>.
Lowering the number
of allowed connections is a temporary workaround for failures,
which are usually confusingly worded <quote>No space
@@ -884,7 +884,7 @@ psql: error: connection to server on socket
"/tmp/.s.PGSQL.5432" failed: No such
When using POSIX semaphores, the number of semaphores needed is the
same as for System V, that is one semaphore per allowed connection
(<xref linkend="guc-max-connections"/>), allowed autovacuum worker process
- (<xref linkend="guc-autovacuum-max-workers"/>), allowed WAL sender process
+ (<xref linkend="guc-autovacuum-worker-slots"/>), allowed WAL sender process
(<xref linkend="guc-max-wal-senders"/>), and allowed background
process (<xref linkend="guc-max-worker-processes"/>).
On the platforms where this option is preferred, there is no specific
diff --git a/src/backend/access/transam/xlog.c
b/src/backend/access/transam/xlog.c
index 330e058c5f..fec72086b9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -5362,7 +5362,7 @@ CheckRequiredParameterValues(void)
*/
if (ArchiveRecoveryRequested && EnableHotStandby)
{
- /* We ignore autovacuum_max_workers when we make this test. */
+ /* We ignore autovacuum_worker_slots when we make this test. */
RecoveryRequiresIntParameter("max_connections",
MaxConnections,
ControlFile->MaxConnections);
diff --git a/src/backend/postmaster/autovacuum.c
b/src/backend/postmaster/autovacuum.c
index 9a925a10cd..5f413305a2 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -114,6 +114,7 @@
* GUC parameters
*/
bool autovacuum_start_daemon = false;
+int autovacuum_worker_slots;
int autovacuum_max_workers;
int autovacuum_work_mem = -1;
int autovacuum_naptime;
@@ -209,7 +210,7 @@ typedef struct autovac_table
/*-------------
* This struct holds information about a single worker's whereabouts. We keep
* an array of these in shared memory, sized according to
- * autovacuum_max_workers.
+ * autovacuum_worker_slots.
*
* wi_links entry into free list or running list
* wi_dboid OID of the database this worker is supposed to work on
@@ -289,7 +290,7 @@ typedef struct
{
sig_atomic_t av_signal[AutoVacNumSignals];
pid_t av_launcherpid;
- dlist_head av_freeWorkers;
+ dclist_head av_freeWorkers;
dlist_head av_runningWorkers;
WorkerInfo av_startingWorker;
AutoVacuumWorkItem av_workItems[NUM_WORKITEMS];
@@ -347,6 +348,7 @@ static void autovac_report_activity(autovac_table *tab);
static void autovac_report_workitem(AutoVacuumWorkItem *workitem,
const
char *nspname, const char *relname);
static void avl_sigusr2_handler(SIGNAL_ARGS);
+static bool av_worker_available(void);
@@ -575,8 +577,7 @@ AutoVacLauncherMain(char *startup_data, size_t
startup_data_len)
* wakening conditions.
*/
-
launcher_determine_sleep(!dlist_is_empty(&AutoVacuumShmem->av_freeWorkers),
- false, &nap);
+ launcher_determine_sleep(av_worker_available(), false, &nap);
/*
* Wait until naptime expires or we get some type of signal
(all the
@@ -636,7 +637,7 @@ AutoVacLauncherMain(char *startup_data, size_t
startup_data_len)
current_time = GetCurrentTimestamp();
LWLockAcquire(AutovacuumLock, LW_SHARED);
- can_launch = !dlist_is_empty(&AutoVacuumShmem->av_freeWorkers);
+ can_launch = av_worker_available();
if (AutoVacuumShmem->av_startingWorker != NULL)
{
@@ -679,8 +680,8 @@ AutoVacLauncherMain(char *startup_data, size_t
startup_data_len)
worker->wi_sharedrel = false;
worker->wi_proc = NULL;
worker->wi_launchtime = 0;
-
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
-
&worker->wi_links);
+
dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
+
&worker->wi_links);
AutoVacuumShmem->av_startingWorker =
NULL;
ereport(WARNING,
errmsg("autovacuum
worker took too long to start; canceled"));
@@ -1087,7 +1088,7 @@ do_start_worker(void)
/* return quickly when there are no free workers */
LWLockAcquire(AutovacuumLock, LW_SHARED);
- if (dlist_is_empty(&AutoVacuumShmem->av_freeWorkers))
+ if (!av_worker_available())
{
LWLockRelease(AutovacuumLock);
return InvalidOid;
@@ -1240,7 +1241,7 @@ do_start_worker(void)
* Get a worker entry from the freelist. We checked above, so
there
* really should be a free slot.
*/
- wptr = dlist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);
+ wptr = dclist_pop_head_node(&AutoVacuumShmem->av_freeWorkers);
worker = dlist_container(WorkerInfoData, wi_links, wptr);
worker->wi_dboid = avdb->adw_datid;
@@ -1609,8 +1610,8 @@ FreeWorkerInfo(int code, Datum arg)
MyWorkerInfo->wi_proc = NULL;
MyWorkerInfo->wi_launchtime = 0;
pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance);
- dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
- &MyWorkerInfo->wi_links);
+ dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
+ &MyWorkerInfo->wi_links);
/* not mine anymore */
MyWorkerInfo = NULL;
@@ -3265,7 +3266,7 @@ AutoVacuumShmemSize(void)
*/
size = sizeof(AutoVacuumShmemStruct);
size = MAXALIGN(size);
- size = add_size(size, mul_size(autovacuum_max_workers,
+ size = add_size(size, mul_size(autovacuum_worker_slots,
sizeof(WorkerInfoData)));
return size;
}
@@ -3292,7 +3293,7 @@ AutoVacuumShmemInit(void)
Assert(!found);
AutoVacuumShmem->av_launcherpid = 0;
- dlist_init(&AutoVacuumShmem->av_freeWorkers);
+ dclist_init(&AutoVacuumShmem->av_freeWorkers);
dlist_init(&AutoVacuumShmem->av_runningWorkers);
AutoVacuumShmem->av_startingWorker = NULL;
memset(AutoVacuumShmem->av_workItems, 0,
@@ -3302,10 +3303,10 @@ AutoVacuumShmemInit(void)
MAXALIGN(sizeof(AutoVacuumShmemStruct)));
/* initialize the WorkerInfo free list */
- for (i = 0; i < autovacuum_max_workers; i++)
+ for (i = 0; i < autovacuum_worker_slots; i++)
{
- dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
- &worker[i].wi_links);
+ dclist_push_head(&AutoVacuumShmem->av_freeWorkers,
+ &worker[i].wi_links);
pg_atomic_init_flag(&worker[i].wi_dobalance);
}
@@ -3341,3 +3342,14 @@ check_autovacuum_work_mem(int *newval, void **extra,
GucSource source)
return true;
}
+
+/*
+ * Returns whether there is a free autovacuum worker slot available.
+ */
+static bool
+av_worker_available(void)
+{
+ int reserved = autovacuum_worker_slots -
autovacuum_max_workers;
+
+ return dclist_count(&AutoVacuumShmem->av_freeWorkers) > Max(0,
reserved);
+}
diff --git a/src/backend/postmaster/postmaster.c
b/src/backend/postmaster/postmaster.c
index bf0241aed0..2588a68fbc 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -4144,7 +4144,7 @@ CreateOptsFile(int argc, char *argv[], char *fullprogname)
int
MaxLivePostmasterChildren(void)
{
- return 2 * (MaxConnections + autovacuum_max_workers + 1 +
+ return 2 * (MaxConnections + autovacuum_worker_slots + 1 +
max_wal_senders + max_worker_processes);
}
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index ce29da9012..80dbd793b5 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -142,7 +142,7 @@ ProcGlobalSemas(void)
* So, now we grab enough semaphores to support the desired max number
* of backends immediately at initialization --- if the sysadmin has set
* MaxConnections, max_worker_processes, max_wal_senders, or
- * autovacuum_max_workers higher than his kernel will support, he'll
+ * autovacuum_worker_slots higher than his kernel will support, he'll
* find out sooner rather than later.
*
* Another reason for creating semaphores here is that the semaphore
@@ -242,13 +242,13 @@ InitProcGlobal(void)
dlist_push_tail(&ProcGlobal->freeProcs, &proc->links);
proc->procgloballist = &ProcGlobal->freeProcs;
}
- else if (i < MaxConnections + autovacuum_max_workers + 1)
+ else if (i < MaxConnections + autovacuum_worker_slots + 1)
{
/* PGPROC for AV launcher/worker, add to
autovacFreeProcs list */
dlist_push_tail(&ProcGlobal->autovacFreeProcs,
&proc->links);
proc->procgloballist = &ProcGlobal->autovacFreeProcs;
}
- else if (i < MaxConnections + autovacuum_max_workers + 1 +
max_worker_processes)
+ else if (i < MaxConnections + autovacuum_worker_slots + 1 +
max_worker_processes)
{
/* PGPROC for bgworker, add to bgworkerFreeProcs list */
dlist_push_tail(&ProcGlobal->bgworkerFreeProcs,
&proc->links);
diff --git a/src/backend/utils/init/postinit.c
b/src/backend/utils/init/postinit.c
index 0805398e24..8fb7753fe0 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -577,7 +577,7 @@ InitializeMaxBackends(void)
Assert(MaxBackends == 0);
/* the extra unit accounts for the autovacuum launcher */
- MaxBackends = MaxConnections + autovacuum_max_workers + 1 +
+ MaxBackends = MaxConnections + autovacuum_worker_slots + 1 +
max_worker_processes + max_wal_senders;
/* internal error because the values were all checked previously */
@@ -591,17 +591,17 @@ InitializeMaxBackends(void)
bool
check_max_connections(int *newval, void **extra, GucSource source)
{
- if (*newval + autovacuum_max_workers + 1 +
+ if (*newval + autovacuum_worker_slots + 1 +
max_worker_processes + max_wal_senders > MAX_BACKENDS)
return false;
return true;
}
/*
- * GUC check_hook for autovacuum_max_workers
+ * GUC check_hook for autovacuum_worker_slots
*/
bool
-check_autovacuum_max_workers(int *newval, void **extra, GucSource source)
+check_autovacuum_worker_slots(int *newval, void **extra, GucSource source)
{
if (MaxConnections + *newval + 1 +
max_worker_processes + max_wal_senders > MAX_BACKENDS)
@@ -615,7 +615,7 @@ check_autovacuum_max_workers(int *newval, void **extra,
GucSource source)
bool
check_max_worker_processes(int *newval, void **extra, GucSource source)
{
- if (MaxConnections + autovacuum_max_workers + 1 +
+ if (MaxConnections + autovacuum_worker_slots + 1 +
*newval + max_wal_senders > MAX_BACKENDS)
return false;
return true;
@@ -627,7 +627,7 @@ check_max_worker_processes(int *newval, void **extra,
GucSource source)
bool
check_max_wal_senders(int *newval, void **extra, GucSource source)
{
- if (MaxConnections + autovacuum_max_workers + 1 +
+ if (MaxConnections + autovacuum_worker_slots + 1 +
max_worker_processes + *newval > MAX_BACKENDS)
return false;
return true;
diff --git a/src/backend/utils/misc/guc_tables.c
b/src/backend/utils/misc/guc_tables.c
index 46c258be28..d9fa3bc8db 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -3381,13 +3381,22 @@ struct config_int ConfigureNamesInt[] =
},
{
/* see max_connections */
- {"autovacuum_max_workers", PGC_POSTMASTER, AUTOVACUUM,
+ {"autovacuum_worker_slots", PGC_POSTMASTER, AUTOVACUUM,
+ gettext_noop("Sets the number of backend slots to
allocate for autovacuum workers."),
+ NULL
+ },
+ &autovacuum_worker_slots,
+ 16, 1, MAX_BACKENDS,
+ check_autovacuum_worker_slots, NULL, NULL
+ },
+ {
+ {"autovacuum_max_workers", PGC_SIGHUP, AUTOVACUUM,
gettext_noop("Sets the maximum number of simultaneously
running autovacuum worker processes."),
NULL
},
&autovacuum_max_workers,
3, 1, MAX_BACKENDS,
- check_autovacuum_max_workers, NULL, NULL
+ NULL, NULL, NULL
},
{
diff --git a/src/backend/utils/misc/postgresql.conf.sample
b/src/backend/utils/misc/postgresql.conf.sample
index e0567de219..4084e80cb9 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -658,8 +658,9 @@
#autovacuum = on # Enable autovacuum subprocess? 'on'
# requires track_counts to also be on.
-#autovacuum_max_workers = 3 # max number of autovacuum subprocesses
+autovacuum_worker_slots = 16 # autovacuum worker slots to allocate
# (change requires restart)
+#autovacuum_max_workers = 3 # max number of autovacuum subprocesses
#autovacuum_naptime = 1min # time between autovacuum runs
#autovacuum_vacuum_threshold = 50 # min number of row updates before
# vacuum
diff --git a/src/include/postmaster/autovacuum.h
b/src/include/postmaster/autovacuum.h
index cae1e8b329..190baa699d 100644
--- a/src/include/postmaster/autovacuum.h
+++ b/src/include/postmaster/autovacuum.h
@@ -28,6 +28,7 @@ typedef enum
/* GUC variables */
extern PGDLLIMPORT bool autovacuum_start_daemon;
+extern PGDLLIMPORT int autovacuum_worker_slots;
extern PGDLLIMPORT int autovacuum_max_workers;
extern PGDLLIMPORT int autovacuum_work_mem;
extern PGDLLIMPORT int autovacuum_naptime;
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index d64dc5fcdb..aa5da2c286 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -29,8 +29,8 @@ extern bool check_application_name(char **newval, void
**extra,
GucSource
source);
extern void assign_application_name(const char *newval, void *extra);
extern const char *show_archive_command(void);
-extern bool check_autovacuum_max_workers(int *newval, void **extra,
-
GucSource source);
+extern bool check_autovacuum_worker_slots(int *newval, void **extra,
+
GucSource source);
extern bool check_autovacuum_work_mem(int *newval, void **extra,
GucSource source);
extern bool check_vacuum_buffer_usage_limit(int *newval, void **extra,
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm
b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 83f385a487..9428e9cd1a 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -608,6 +608,7 @@ sub init
}
print $conf "max_wal_senders = 10\n";
print $conf "max_replication_slots = 10\n";
+ print $conf "autovacuum_worker_slots = 3\n";
print $conf "wal_log_hints = on\n";
print $conf "hot_standby = on\n";
# conservative settings to ensure we can run multiple
postmasters:
--
2.39.3 (Apple Git-146)
