On Sat, Mar 25, 2023 at 3:03 PM Melanie Plageman
<melanieplage...@gmail.com> wrote:
>
> On Thu, Mar 23, 2023 at 8:27 PM Melanie Plageman
> <melanieplage...@gmail.com> wrote:
> > On Thu, Mar 23, 2023 at 2:09 AM Masahiko Sawada <sawada.m...@gmail.com>
> > wrote:
> > > > And, I was wondering if it was worth trying to split up the part that
> > > > reloads the config file and all of the autovacuum stuff. The reloading
> > > > of the config file by itself won't actually result in autovacuum workers
> > > > having updated cost delays because of them overwriting it with
> > > > wi_cost_delay, but it will allow VACUUM to have those updated values.
> > >
> > > It makes sense to me to have changes for overhauling the rebalance
> > > mechanism in a separate patch.
> > >
> > > Looking back at the original concern you mentioned[1]:
> > >
> > > speed up long-running vacuum of a large table by
> > > decreasing autovacuum_vacuum_cost_delay/vacuum_cost_delay, however the
> > > config file is only reloaded between tables (for autovacuum) or after
> > > the statement (for explicit vacuum).
> > >
> > > does it make sense to have autovac_balance_cost() update workers'
> > > wi_cost_delay too? Autovacuum launcher already reloads the config file
> > > and does the rebalance. So I thought autovac_balance_cost() can update
> > > the cost_delay as well, and this might be a minimal change to deal
> > > with your concern. This doesn't have the effect for manual VACUUM but
> > > since vacuum delay is disabled by default it won't be a big problem.
> > > As for manual VACUUMs, we would need to reload the config file in
> > > vacuum_delay_point() as the part of your patch does. Overhauling the
> > > rebalance mechanism would be another patch to improve it further.
> >
> > So, we can't do this without acquiring an access shared lock on every
> > call to vacuum_delay_point() because cost delay is a double.
> >
> > I will work on a patchset with separate commits for reloading the config
> > file, though (with autovac not benefitting in the first commit).
>
> So, I realized we could actually do as you say and have autovac workers
> update their wi_cost_delay and keep the balance changes in a separate
> commit. I've done this in attached v8.
>
> Workers take the exclusive lock to update their wi_cost_delay and
> wi_cost_limit only when there is a config reload. So, there is one
> commit that implements this behavior and a separate commit to revise the
> worker rebalancing.
So, I've attached an alternate version of the patchset which takes the
approach of having one commit which only enables cost-based delay GUC
refresh for VACUUM and another commit which enables it for autovacuum
and makes the changes to balancing variables.
I still think the commit which has workers updating their own
wi_cost_delay in vacuum_delay_point() is a bit weird. It relies on no one
else emulating our bad behavior and reading from wi_cost_delay without a
lock and on no one else deciding to ever write to wi_cost_delay (even
though it is in shared memory [this is the same as master]). It is only
safe because our process is the only one (right now) writing to
wi_cost_delay, so when we read from it without a lock, we know it isn't
being written to. And everyone else takes a lock when reading from
wi_cost_delay right now. So, it seems...not great.
This approach also introduces a function that is only around for
one commit until the next commit obsoletes it, which seems a bit silly.
Basically, I think it is probably better to just have one commit
enabling guc refresh for VACUUM and then another which correctly
implements what is needed for autovacuum to do the same.
Attached v9 does this.
I've provided both complete versions of both approaches (v9 and v8).
- Melanie
From 94c08c1b764619ad6cc3a0c75295f416e1863b26 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Sat, 25 Mar 2023 11:59:33 -0400
Subject: [PATCH v9 1/4] Zero out VacuumCostBalance
Though it is unlikely to matter, we should zero out VacuumCostBalance
whenever we may be transitioning the state of VacuumCostActive to false.
---
src/backend/commands/vacuum.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index c54360a6a0..7d01df7e48 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -550,6 +550,7 @@ vacuum(List *relations, VacuumParams *params,
{
in_vacuum = false;
VacuumCostActive = false;
+ VacuumCostBalance = 0;
}
PG_END_TRY();
--
2.37.2
From 3bdf9414c5840bcc94a9c0292f25ec41d2e95b69 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Sat, 25 Mar 2023 14:14:55 -0400
Subject: [PATCH v9 4/4] Autovacuum refreshes cost-based delay params more
often
The previous commit allowed VACUUM to reload the config file more often
so that cost-based delay parameters could take effect while VACUUMing a
relation. Autovacuum, however did not benefit from this change.
In order for autovacuum workers to safely update their own cost delay
and cost limit parameters without impacting performance, we had to
rethink when and how these values were accessed.
Previously, an autovacuum worker's wi_cost_limit was set only at the
beginning of vacuuming a table, after reloading the config file.
Therefore, at the time that autovac_balance_cost() is called, workers
vacuuming tables with no table options could still have different values
for their wi_cost_limit_base and wi_cost_delay.
Now that the cost parameters can be updated while vacuuming a table,
workers will (within some margin of error) have no reason to have
different values for cost limit and cost delay (in the absence of table
options). This removes the rationale for keeping cost limit and cost
delay in shared memory. Balancing the cost limit requires only the
number of active autovacuum workers vacuuming a table with no cost-based
table options.
---
src/backend/commands/vacuum.c | 24 ++-
src/backend/postmaster/autovacuum.c | 228 +++++++++++++---------------
src/include/postmaster/autovacuum.h | 1 +
3 files changed, 124 insertions(+), 129 deletions(-)
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 0e686c94b2..8e39a13285 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -2241,11 +2241,11 @@ vacuum_delay_point(void)
/*
* Reload the configuration file if requested. This allows changes to
- * vacuum_cost_limit and vacuum_cost_delay to take effect while a table is
- * being vacuumed or analyzed. Analyze should not reload configuration
- * file if it is in an outer transaction, as GUC values shouldn't be
- * allowed to refer to some uncommitted state (e.g. database objects
- * created in this transaction).
+ * [autovacuum]_vacuum_cost_limit and [autovacuum]_vacuum_cost_delay to
+ * take effect while a table is being vacuumed or analyzed. Analyze should
+ * not reload configuration file if it is in an outer transaction, as GUC
+ * values shouldn't be allowed to refer to some uncommitted state (e.g.
+ * database objects created in this transaction).
*/
if (ConfigReloadPending && !analyze_in_outer_xact)
{
@@ -2258,10 +2258,12 @@ vacuum_delay_point(void)
* by reload.
*/
AutoVacuumUpdateDelay();
+ AutoVacuumUpdateLimit();
/*
* If configuration changes are allowed to impact VacuumCostInactive,
- * make sure it is updated.
+ * make sure it is updated. Autovacuum workers will have already done
+ * this in AutoVacuumUpdateDelay()
*/
if (VacuumCostInactive == VACUUM_COST_INACTIVE_AND_LOCKED)
return;
@@ -2312,8 +2314,14 @@ vacuum_delay_point(void)
VacuumCostBalance = 0;
- /* update balance values for workers */
- AutoVacuumUpdateDelay();
+ /*
+ * Update limit values for autovacuum workers. We must always do this
+ * in case the autovacuum launcher or another autovacuum worker has
+ * recalculated the number of workers across which we must balance the
+ * limit. This is done by the launcher when launching a new worker and
+ * by workers before vacuuming each table.
+ */
+ AutoVacuumUpdateLimit();
/* Might have gotten an interrupt while sleeping */
CHECK_FOR_INTERRUPTS();
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 585d28148c..6fe16aca3a 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -139,6 +139,9 @@ int Log_autovacuum_min_duration = 600000;
static bool am_autovacuum_launcher = false;
static bool am_autovacuum_worker = false;
+static double av_table_option_cost_delay = -1;
+static int av_table_option_cost_limit = 0;
+
/* Flags set by signal handlers */
static volatile sig_atomic_t got_SIGUSR2 = false;
@@ -189,8 +192,8 @@ typedef struct autovac_table
{
Oid at_relid;
VacuumParams at_params;
- double at_vacuum_cost_delay;
- int at_vacuum_cost_limit;
+ double at_table_option_vac_cost_delay;
+ int at_table_option_vac_cost_limit;
bool at_dobalance;
bool at_sharedrel;
char *at_relname;
@@ -209,7 +212,7 @@ typedef struct autovac_table
* wi_sharedrel flag indicating whether table is marked relisshared
* wi_proc pointer to PGPROC of the running worker, NULL if not started
* wi_launchtime Time at which this worker was launched
- * wi_cost_* Vacuum cost-based delay parameters current in this worker
+ * wi_dobalance Whether this worker should be included in balance calculations
*
* All fields are protected by AutovacuumLock, except for wi_tableoid and
* wi_sharedrel which are protected by AutovacuumScheduleLock (note these
@@ -225,9 +228,6 @@ typedef struct WorkerInfoData
TimestampTz wi_launchtime;
bool wi_dobalance;
bool wi_sharedrel;
- double wi_cost_delay;
- int wi_cost_limit;
- int wi_cost_limit_base;
} WorkerInfoData;
typedef struct WorkerInfoData *WorkerInfo;
@@ -273,6 +273,8 @@ typedef struct AutoVacuumWorkItem
* av_startingWorker pointer to WorkerInfo currently being started (cleared by
* the worker itself as soon as it's up and running)
* av_workItems work item array
+ * av_nworkers_for_balance the number of autovacuum workers to use when
+ * calculating the per worker cost limit
*
* This struct is protected by AutovacuumLock, except for av_signal and parts
* of the worker list (see above).
@@ -286,6 +288,7 @@ typedef struct
dlist_head av_runningWorkers;
WorkerInfo av_startingWorker;
AutoVacuumWorkItem av_workItems[NUM_WORKITEMS];
+ pg_atomic_uint32 av_nworkers_for_balance;
} AutoVacuumShmemStruct;
static AutoVacuumShmemStruct *AutoVacuumShmem;
@@ -820,7 +823,7 @@ HandleAutoVacLauncherInterrupts(void)
AutoVacLauncherShutdown();
/* rebalance in case the default cost parameters changed */
- LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
+ LWLockAcquire(AutovacuumLock, LW_SHARED);
autovac_balance_cost();
LWLockRelease(AutovacuumLock);
@@ -1756,9 +1759,6 @@ FreeWorkerInfo(int code, Datum arg)
MyWorkerInfo->wi_proc = NULL;
MyWorkerInfo->wi_launchtime = 0;
MyWorkerInfo->wi_dobalance = false;
- MyWorkerInfo->wi_cost_delay = 0;
- MyWorkerInfo->wi_cost_limit = 0;
- MyWorkerInfo->wi_cost_limit_base = 0;
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&MyWorkerInfo->wi_links);
/* not mine anymore */
@@ -1773,100 +1773,114 @@ FreeWorkerInfo(int code, Datum arg)
}
}
+
/*
- * Update the cost-based delay parameters, so that multiple workers consume
- * each a fraction of the total available I/O.
+ * Update VacuumCostDelay with the correct value for an autovacuum worker,
+ * given the value of other relevant cost-based delay parameters. Autovacuum
+ * workers should call this after every config reload, in case VacuumCostDelay
+ * was overwritten.
*/
void
AutoVacuumUpdateDelay(void)
{
- if (MyWorkerInfo)
+ if (!am_autovacuum_worker)
+ return;
+
+ if (av_table_option_cost_delay >= 0)
+ VacuumCostDelay = av_table_option_cost_delay;
+ else if (autovacuum_vac_cost_delay >= 0)
+ VacuumCostDelay = autovacuum_vac_cost_delay;
+
+ /*
+ * If configuration changes are allowed to impact VacuumCostInactive, make
+ * sure it is updated.
+ */
+ if (VacuumCostInactive == VACUUM_COST_INACTIVE_AND_LOCKED)
+ return;
+
+ if (VacuumCostDelay > 0)
+ VacuumCostInactive = VACUUM_COST_ACTIVE;
+ else
{
- VacuumCostDelay = MyWorkerInfo->wi_cost_delay;
- VacuumCostLimit = MyWorkerInfo->wi_cost_limit;
+ VacuumCostInactive = VACUUM_COST_INACTIVE_AND_UNLOCKED;
+ VacuumCostBalance = 0;
}
}
+
/*
- * autovac_balance_cost
- * Recalculate the cost limit setting for each active worker.
- *
- * Caller must hold the AutovacuumLock in exclusive mode.
+ * Update VacuumCostLimit with the correct value for an autovacuum worker,
+ * given the value of other relevant cost limit parameters and the number of
+ * workers across which the limit must be balanced. Autovacuum workers must
+ * call this regularly in case av_nworkers_for_balance has been updated by
+ * another worker or by the autovacuum launcher. They also must call this after
+ * every config reload, in case VacuumCostLimit was overwritten.
*/
-static void
-autovac_balance_cost(void)
+void
+AutoVacuumUpdateLimit(void)
{
+ if (!am_autovacuum_worker)
+ return;
+
/*
- * The idea here is that we ration out I/O equally. The amount of I/O
- * that a worker can consume is determined by cost_limit/cost_delay, so we
- * try to equalize those ratios rather than the raw limit settings.
- *
* note: in cost_limit, zero also means use value from elsewhere, because
* zero is not a valid value.
*/
- int vac_cost_limit = (autovacuum_vac_cost_limit > 0 ?
- autovacuum_vac_cost_limit : VacuumCostLimit);
- double vac_cost_delay = (autovacuum_vac_cost_delay >= 0 ?
- autovacuum_vac_cost_delay : VacuumCostDelay);
- double cost_total;
- double cost_avail;
- dlist_iter iter;
+ if (av_table_option_cost_limit > 0)
+ VacuumCostLimit = av_table_option_cost_limit;
+ else
+ {
+ /* There is at least 1 autovac worker (this worker). */
+ int nworkers_for_balance = Max(pg_atomic_read_u32(
+ &AutoVacuumShmem->av_nworkers_for_balance), 1);
- /* not set? nothing to do */
- if (vac_cost_limit <= 0 || vac_cost_delay <= 0)
- return;
+ int vac_cost_limit = autovacuum_vac_cost_limit > 0 ?
+ autovacuum_vac_cost_limit : VacuumCostLimit;
- /* calculate the total base cost limit of participating active workers */
- cost_total = 0.0;
- dlist_foreach(iter, &AutoVacuumShmem->av_runningWorkers)
- {
- WorkerInfo worker = dlist_container(WorkerInfoData, wi_links, iter.cur);
+ int balanced_cost_limit = vac_cost_limit / nworkers_for_balance;
- if (worker->wi_proc != NULL &&
- worker->wi_dobalance &&
- worker->wi_cost_limit_base > 0 && worker->wi_cost_delay > 0)
- cost_total +=
- (double) worker->wi_cost_limit_base / worker->wi_cost_delay;
+ VacuumCostLimit = Max(Min(balanced_cost_limit, vac_cost_limit), 1);
}
+}
- /* there are no cost limits -- nothing to do */
- if (cost_total <= 0)
+
+/*
+ * autovac_balance_cost
+ * Recalculate the number of workers to consider, given table options and
+ * the current number of active workers.
+ *
+ * Caller must hold the AutovacuumLock in at least shared mode.
+ */
+static void
+autovac_balance_cost(void)
+{
+ dlist_iter iter;
+ int orig_nworkers_for_balance;
+ int nworkers_for_balance = 0;
+
+ if (autovacuum_vac_cost_delay == 0 ||
+ (autovacuum_vac_cost_delay == -1 && VacuumCostDelay == 0))
return;
- /*
- * Adjust cost limit of each active worker to balance the total of cost
- * limit to autovacuum_vacuum_cost_limit.
- */
- cost_avail = (double) vac_cost_limit / vac_cost_delay;
+ if (autovacuum_vac_cost_limit <= 0 && VacuumCostLimit <= 0)
+ return;
+
+ orig_nworkers_for_balance =
+ pg_atomic_read_u32(&AutoVacuumShmem->av_nworkers_for_balance);
+
dlist_foreach(iter, &AutoVacuumShmem->av_runningWorkers)
{
WorkerInfo worker = dlist_container(WorkerInfoData, wi_links, iter.cur);
- if (worker->wi_proc != NULL &&
- worker->wi_dobalance &&
- worker->wi_cost_limit_base > 0 && worker->wi_cost_delay > 0)
- {
- int limit = (int)
- (cost_avail * worker->wi_cost_limit_base / cost_total);
-
- /*
- * We put a lower bound of 1 on the cost_limit, to avoid division-
- * by-zero in the vacuum code. Also, in case of roundoff trouble
- * in these calculations, let's be sure we don't ever set
- * cost_limit to more than the base value.
- */
- worker->wi_cost_limit = Max(Min(limit,
- worker->wi_cost_limit_base),
- 1);
- }
+ if (worker->wi_proc == NULL || !worker->wi_dobalance)
+ continue;
- if (worker->wi_proc != NULL)
- elog(DEBUG2, "autovac_balance_cost(pid=%d db=%u, rel=%u, dobalance=%s cost_limit=%d, cost_limit_base=%d, cost_delay=%g)",
- worker->wi_proc->pid, worker->wi_dboid, worker->wi_tableoid,
- worker->wi_dobalance ? "yes" : "no",
- worker->wi_cost_limit, worker->wi_cost_limit_base,
- worker->wi_cost_delay);
+ nworkers_for_balance++;
}
+
+ if (nworkers_for_balance != orig_nworkers_for_balance)
+ pg_atomic_write_u32(&AutoVacuumShmem->av_nworkers_for_balance,
+ nworkers_for_balance);
}
/*
@@ -2312,8 +2326,6 @@ do_autovacuum(void)
autovac_table *tab;
bool isshared;
bool skipit;
- double stdVacuumCostDelay;
- int stdVacuumCostLimit;
dlist_iter iter;
CHECK_FOR_INTERRUPTS();
@@ -2416,31 +2428,17 @@ do_autovacuum(void)
continue;
}
- /*
- * Remember the prevailing values of the vacuum cost GUCs. We have to
- * restore these at the bottom of the loop, else we'll compute wrong
- * values in the next iteration of autovac_balance_cost().
- */
- stdVacuumCostDelay = VacuumCostDelay;
- stdVacuumCostLimit = VacuumCostLimit;
+ av_table_option_cost_limit = tab->at_table_option_vac_cost_limit;
+ av_table_option_cost_delay = tab->at_table_option_vac_cost_delay;
/* Must hold AutovacuumLock while mucking with cost balance info */
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
-
- /* advertise my cost delay parameters for the balancing algorithm */
MyWorkerInfo->wi_dobalance = tab->at_dobalance;
- MyWorkerInfo->wi_cost_delay = tab->at_vacuum_cost_delay;
- MyWorkerInfo->wi_cost_limit = tab->at_vacuum_cost_limit;
- MyWorkerInfo->wi_cost_limit_base = tab->at_vacuum_cost_limit;
-
- /* do a balance */
autovac_balance_cost();
+ LWLockRelease(AutovacuumLock);
- /* set the active cost parameters from the result of that */
AutoVacuumUpdateDelay();
-
- /* done */
- LWLockRelease(AutovacuumLock);
+ AutoVacuumUpdateLimit();
/* clean up memory before each iteration */
MemoryContextResetAndDeleteChildren(PortalContext);
@@ -2525,19 +2523,15 @@ deleted:
/*
* Remove my info from shared memory. We could, but intentionally
- * don't, clear wi_cost_limit and friends --- this is on the
- * assumption that we probably have more to do with similar cost
- * settings, so we don't want to give up our share of I/O for a very
- * short interval and thereby thrash the global balance.
+ * don't, set wi_dobalance to false on the assumption that we are more
+ * likely than not to vacuum a table with no table options next, so we
+ * don't want to give up our share of I/O for a very short interval
+ * and thereby thrash the global balance.
*/
LWLockAcquire(AutovacuumScheduleLock, LW_EXCLUSIVE);
MyWorkerInfo->wi_tableoid = InvalidOid;
MyWorkerInfo->wi_sharedrel = false;
LWLockRelease(AutovacuumScheduleLock);
-
- /* restore vacuum cost GUCs for the next iteration */
- VacuumCostDelay = stdVacuumCostDelay;
- VacuumCostLimit = stdVacuumCostLimit;
}
/*
@@ -2569,6 +2563,8 @@ deleted:
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
+ AutoVacuumUpdateDelay();
+ AutoVacuumUpdateLimit();
}
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
@@ -2804,8 +2800,6 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
int freeze_table_age;
int multixact_freeze_min_age;
int multixact_freeze_table_age;
- int vac_cost_limit;
- double vac_cost_delay;
int log_min_duration;
/*
@@ -2815,20 +2809,6 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
* defaults, autovacuum's own first and plain vacuum second.
*/
- /* -1 in autovac setting means use plain vacuum_cost_delay */
- vac_cost_delay = (avopts && avopts->vacuum_cost_delay >= 0)
- ? avopts->vacuum_cost_delay
- : (autovacuum_vac_cost_delay >= 0)
- ? autovacuum_vac_cost_delay
- : VacuumCostDelay;
-
- /* 0 or -1 in autovac setting means use plain vacuum_cost_limit */
- vac_cost_limit = (avopts && avopts->vacuum_cost_limit > 0)
- ? avopts->vacuum_cost_limit
- : (autovacuum_vac_cost_limit > 0)
- ? autovacuum_vac_cost_limit
- : VacuumCostLimit;
-
/* -1 in autovac setting means use log_autovacuum_min_duration */
log_min_duration = (avopts && avopts->log_min_duration >= 0)
? avopts->log_min_duration
@@ -2884,8 +2864,10 @@ table_recheck_autovac(Oid relid, HTAB *table_toast_map,
tab->at_params.multixact_freeze_table_age = multixact_freeze_table_age;
tab->at_params.is_wraparound = wraparound;
tab->at_params.log_min_duration = log_min_duration;
- tab->at_vacuum_cost_limit = vac_cost_limit;
- tab->at_vacuum_cost_delay = vac_cost_delay;
+ tab->at_table_option_vac_cost_limit = avopts ?
+ avopts->vacuum_cost_limit : 0;
+ tab->at_table_option_vac_cost_delay = avopts ?
+ avopts->vacuum_cost_delay : -1;
tab->at_relname = NULL;
tab->at_nspname = NULL;
tab->at_datname = NULL;
@@ -3377,10 +3359,14 @@ AutoVacuumShmemInit(void)
worker = (WorkerInfo) ((char *) AutoVacuumShmem +
MAXALIGN(sizeof(AutoVacuumShmemStruct)));
+
/* initialize the WorkerInfo free list */
for (i = 0; i < autovacuum_max_workers; i++)
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&worker[i].wi_links);
+
+ pg_atomic_init_u32(&AutoVacuumShmem->av_nworkers_for_balance, 0);
+
}
else
Assert(found);
diff --git a/src/include/postmaster/autovacuum.h b/src/include/postmaster/autovacuum.h
index c140371b51..7b462866c9 100644
--- a/src/include/postmaster/autovacuum.h
+++ b/src/include/postmaster/autovacuum.h
@@ -65,6 +65,7 @@ extern void AutoVacWorkerFailed(void);
/* autovacuum cost-delay balancer */
extern void AutoVacuumUpdateDelay(void);
+extern void AutoVacuumUpdateLimit(void);
#ifdef EXEC_BACKEND
extern void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_noreturn();
--
2.37.2
From 28d33a9d5cab0d384a18dbc2bb4ad95da61741c3 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Mon, 27 Mar 2023 13:33:19 -0400
Subject: [PATCH v9 3/4] VACUUM reloads config file more often
Previously, VACUUM would not reload the configuration file. So, changes
to cost-based delay parameters could only take effect on the next
invocation of VACUUM.
Check if a reload is pending roughly once per block now, when checking
if we need to delay.
Note that autovacuum is unaffected by this change. Autovacuum workers
overwrite the value of VacuumCostLimit and VacuumCostDelay with their
own WorkerInfo->wi_cost_limit and wi_cost_delay. Writing to their
wi_cost_delay more often makes reading wi_cost_delay without a lock to
update VacuumCostDelay an even worse idea.
Reviewed-by: Masahiko Sawada <sawada.m...@gmail.com>
Reviewed-by: Daniel Gustafsson <dan...@yesql.se>
Discussion: https://www.postgresql.org/message-id/flat/CAAKRu_buP5wzsho3qNw5o9_R0pF69FRM5hgCmr-mvXmGXwdA7A%40mail.gmail.com#5e6771d4cdca4db6efc2acec2dce0bc7
---
src/backend/commands/vacuum.c | 62 ++++++++++++++++++++++++++++++-----
1 file changed, 54 insertions(+), 8 deletions(-)
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index eb126f2247..0e686c94b2 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -48,6 +48,7 @@
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/bgworker_internals.h"
+#include "postmaster/interrupt.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/pmsignal.h"
@@ -76,6 +77,7 @@ int vacuum_multixact_failsafe_age;
/* A few variables that don't seem worth passing around as parameters */
static MemoryContext vac_context = NULL;
static BufferAccessStrategy vac_strategy;
+static bool analyze_in_outer_xact = false;
/*
@@ -314,8 +316,7 @@ vacuum(List *relations, VacuumParams *params,
static bool in_vacuum = false;
const char *stmttype;
- volatile bool in_outer_xact,
- use_own_xacts;
+ volatile bool use_own_xacts;
Assert(params != NULL);
@@ -332,10 +333,10 @@ vacuum(List *relations, VacuumParams *params,
if (params->options & VACOPT_VACUUM)
{
PreventInTransactionBlock(isTopLevel, stmttype);
- in_outer_xact = false;
+ analyze_in_outer_xact = false;
}
else
- in_outer_xact = IsInTransactionBlock(isTopLevel);
+ analyze_in_outer_xact = IsInTransactionBlock(isTopLevel);
/*
* Due to static variables vac_context, anl_context and vac_strategy,
@@ -457,7 +458,7 @@ vacuum(List *relations, VacuumParams *params,
Assert(params->options & VACOPT_ANALYZE);
if (IsAutoVacuumWorkerProcess())
use_own_xacts = true;
- else if (in_outer_xact)
+ else if (analyze_in_outer_xact)
use_own_xacts = false;
else if (list_length(relations) > 1)
use_own_xacts = true;
@@ -475,7 +476,7 @@ vacuum(List *relations, VacuumParams *params,
*/
if (use_own_xacts)
{
- Assert(!in_outer_xact);
+ Assert(!analyze_in_outer_xact);
/* ActiveSnapshot is not set by autovacuum */
if (ActiveSnapshotSet())
@@ -544,7 +545,7 @@ vacuum(List *relations, VacuumParams *params,
}
analyze_rel(vrel->oid, vrel->relation, params,
- vrel->va_cols, in_outer_xact, vac_strategy);
+ vrel->va_cols, analyze_in_outer_xact, vac_strategy);
if (use_own_xacts)
{
@@ -568,6 +569,7 @@ vacuum(List *relations, VacuumParams *params,
in_vacuum = false;
VacuumCostInactive = VACUUM_COST_INACTIVE_AND_UNLOCKED;
VacuumCostBalance = 0;
+ analyze_in_outer_xact = false;
}
PG_END_TRY();
@@ -2233,7 +2235,51 @@ vacuum_delay_point(void)
/* Always check for interrupts */
CHECK_FOR_INTERRUPTS();
- if (VacuumCostInactive || InterruptPending)
+ if (InterruptPending ||
+ (VacuumCostInactive && !ConfigReloadPending))
+ return;
+
+ /*
+ * Reload the configuration file if requested. This allows changes to
+ * vacuum_cost_limit and vacuum_cost_delay to take effect while a table is
+ * being vacuumed or analyzed. Analyze should not reload configuration
+ * file if it is in an outer transaction, as GUC values shouldn't be
+ * allowed to refer to some uncommitted state (e.g. database objects
+ * created in this transaction).
+ */
+ if (ConfigReloadPending && !analyze_in_outer_xact)
+ {
+ ConfigReloadPending = false;
+ ProcessConfigFile(PGC_SIGHUP);
+
+ /*
+ * Autovacuum workers must restore the correct values of
+ * VacuumCostLimit and VacuumCostDelay in case they were overwritten
+ * by reload.
+ */
+ AutoVacuumUpdateDelay();
+
+ /*
+ * If configuration changes are allowed to impact VacuumCostInactive,
+ * make sure it is updated.
+ */
+ if (VacuumCostInactive == VACUUM_COST_INACTIVE_AND_LOCKED)
+ return;
+
+ if (VacuumCostDelay > 0)
+ VacuumCostInactive = VACUUM_COST_ACTIVE;
+ else
+ {
+ VacuumCostInactive = VACUUM_COST_INACTIVE_AND_UNLOCKED;
+ VacuumCostBalance = 0;
+ }
+ }
+
+ /*
+ * If we disabled cost-based delays after reloading the config file,
+ * return.
+ */
+ if (VacuumCostInactive)
return;
/*
--
2.37.2
From 57a5284abc43fa5531574f998ac2ab8d038264d1 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplage...@gmail.com>
Date: Sat, 25 Mar 2023 12:05:18 -0400
Subject: [PATCH v9 2/4] Make VacuumCostActive failsafe-aware
While vacuuming a table in failsafe mode, VacuumCostActive should not be
re-enabled. This currently isn't a problem because vacuum cost
parameters are only refreshed in between vacuuming tables and failsafe
status is reset for every table. In preparation for allowing vacuum cost
parameters to be updated more frequently, make vacuum cost status more
expressive.
VacuumCostActive is now VacuumCostInactive, as it can only be active in
one way but it can be inactive in two ways. If performing a failsafe
vacuum, the vacuum cost status cannot be enabled and is effectively
"locked". If performing a non-failsafe vacuum, the vacuum cost status
may be active or inactive. To express this, VacuumCostInactive can be
one of three statuses: VACUUM_COST_INACTIVE_AND_LOCKED,
VACUUM_COST_ACTIVE_AND_LOCKED, and VACUUM_COST_ACTIVE.
VacuumCostInactive is defined as an integer because we do not want
non-vacuum code concerning itself with the distinction between the three
statuses -- only with whether or not VacuumCostInactive == 0 or not.
---
src/backend/access/heap/vacuumlazy.c | 2 +-
src/backend/commands/vacuum.c | 23 ++++++++++++++++++++---
src/backend/commands/vacuumparallel.c | 8 ++++++--
src/backend/storage/buffer/bufmgr.c | 8 ++++----
src/backend/utils/init/globals.c | 2 +-
src/include/commands/vacuum.h | 8 ++++++++
src/include/miscadmin.h | 3 +--
7 files changed, 41 insertions(+), 13 deletions(-)
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 8f14cf85f3..040a4e931b 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -2637,7 +2637,7 @@ lazy_check_wraparound_failsafe(LVRelState *vacrel)
"You might also need to consider other ways for VACUUM to keep up with the allocation of transaction IDs.")));
/* Stop applying cost limits from this point on */
- VacuumCostActive = false;
+ VacuumCostInactive = VACUUM_COST_INACTIVE_AND_LOCKED;
VacuumCostBalance = 0;
return true;
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 7d01df7e48..eb126f2247 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -491,7 +491,6 @@ vacuum(List *relations, VacuumParams *params,
ListCell *cur;
in_vacuum = true;
- VacuumCostActive = (VacuumCostDelay > 0);
VacuumCostBalance = 0;
VacuumPageHit = 0;
VacuumPageMiss = 0;
@@ -507,6 +506,24 @@ vacuum(List *relations, VacuumParams *params,
{
VacuumRelation *vrel = lfirst_node(VacuumRelation, cur);
+ /*
+ * failsafe_active is reset per relation, so we must be sure that
+ * VacuumCostInactive is set to either VACUUM_COST_INACTIVE or
+ * VACUUM_COST_INACTIVE_AND_UNLOCKED in between vacuuming
+ * relations.
+ */
+ VacuumCostInactive = VacuumCostDelay > 0 ? VACUUM_COST_ACTIVE :
+ VACUUM_COST_INACTIVE_AND_UNLOCKED;
+
+ /*
+ * We should not have transitioned VacuumCostInactive from
+ * VACUUM_COST_ACTIVE to VACUUM_COST_INACTIVE_AND_UNLOCKED above,
+ * as that should have happened when we changed the value of
+ * VacuumCostDelay.
+ */
+ Assert(VacuumCostInactive == VACUUM_COST_ACTIVE ||
+ VacuumCostBalance == 0);
+
if (params->options & VACOPT_VACUUM)
{
if (!vacuum_rel(vrel->oid, vrel->relation, params, false))
@@ -549,7 +566,7 @@ vacuum(List *relations, VacuumParams *params,
PG_FINALLY();
{
in_vacuum = false;
- VacuumCostActive = false;
+ VacuumCostInactive = VACUUM_COST_INACTIVE_AND_UNLOCKED;
VacuumCostBalance = 0;
}
PG_END_TRY();
@@ -2216,7 +2233,7 @@ vacuum_delay_point(void)
/* Always check for interrupts */
CHECK_FOR_INTERRUPTS();
- if (!VacuumCostActive || InterruptPending)
+ if (VacuumCostInactive || InterruptPending)
return;
/*
diff --git a/src/backend/commands/vacuumparallel.c b/src/backend/commands/vacuumparallel.c
index bcd40c80a1..266bf6bb4c 100644
--- a/src/backend/commands/vacuumparallel.c
+++ b/src/backend/commands/vacuumparallel.c
@@ -989,8 +989,12 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
PARALLEL_VACUUM_KEY_DEAD_ITEMS,
false);
- /* Set cost-based vacuum delay */
- VacuumCostActive = (VacuumCostDelay > 0);
+ /*
+ * Set cost-based vacuum delay Parallel vacuum workers will not execute
+ * failsafe VACUUM.
+ */
+ VacuumCostInactive = VacuumCostDelay > 0 ? VACUUM_COST_ACTIVE :
+ VACUUM_COST_INACTIVE_AND_UNLOCKED;
VacuumCostBalance = 0;
VacuumPageHit = 0;
VacuumPageMiss = 0;
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 95212a3941..6d3dd26fc7 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -893,7 +893,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
*hit = true;
VacuumPageHit++;
- if (VacuumCostActive)
+ if (!VacuumCostInactive)
VacuumCostBalance += VacuumCostPageHit;
TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
@@ -1098,7 +1098,7 @@ ReadBuffer_common(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
}
VacuumPageMiss++;
- if (VacuumCostActive)
+ if (!VacuumCostInactive)
VacuumCostBalance += VacuumCostPageMiss;
TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
@@ -1672,7 +1672,7 @@ MarkBufferDirty(Buffer buffer)
{
VacuumPageDirty++;
pgBufferUsage.shared_blks_dirtied++;
- if (VacuumCostActive)
+ if (!VacuumCostInactive)
VacuumCostBalance += VacuumCostPageDirty;
}
}
@@ -4199,7 +4199,7 @@ MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
{
VacuumPageDirty++;
pgBufferUsage.shared_blks_dirtied++;
- if (VacuumCostActive)
+ if (!VacuumCostInactive)
VacuumCostBalance += VacuumCostPageDirty;
}
}
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 1b1d814254..608ebb9182 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -150,4 +150,4 @@ int64 VacuumPageMiss = 0;
int64 VacuumPageDirty = 0;
int VacuumCostBalance = 0; /* working state for vacuum */
-bool VacuumCostActive = false;
+int VacuumCostInactive = 1;
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index bdfd96cfec..5c3e250b06 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -302,6 +302,14 @@ extern PGDLLIMPORT int vacuum_failsafe_age;
extern PGDLLIMPORT int vacuum_multixact_failsafe_age;
/* Variables for cost-based parallel vacuum */
+
+typedef enum VacuumCostStatus
+{
+ VACUUM_COST_INACTIVE_AND_LOCKED = -1,
+ VACUUM_COST_ACTIVE = 0,
+ VACUUM_COST_INACTIVE_AND_UNLOCKED = 1,
+} VacuumCostStatus;
+
extern PGDLLIMPORT pg_atomic_uint32 *VacuumSharedCostBalance;
extern PGDLLIMPORT pg_atomic_uint32 *VacuumActiveNWorkers;
extern PGDLLIMPORT int VacuumCostBalanceLocal;
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 06a86f9ac1..33e22733ae 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -274,8 +274,7 @@ extern PGDLLIMPORT int64 VacuumPageMiss;
extern PGDLLIMPORT int64 VacuumPageDirty;
extern PGDLLIMPORT int VacuumCostBalance;
-extern PGDLLIMPORT bool VacuumCostActive;
-
+extern PGDLLIMPORT int VacuumCostInactive;
/* in tcop/postgres.c */
--
2.37.2
