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Refresh cost-based delay params more frequently in autovacuum 

Allow autovacuum to reload the config file more often so that cost-based
delay parameters can take effect while VACUUMing a relation. Previously,
autovacuum workers only reloaded the config file once per relation
vacuumed, so config changes could not take effect until beginning to
vacuum the next table.

Now, check if a reload is pending roughly once per block, when checking
if we need to delay.

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() was called, workers
vacuuming tables with no cost-related storage parameters 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
cost-related storage parameters). 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 storage parameters.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAAKRu_ZngzqnEODc7LmS1NH04Kt6Y9huSjz5pp7%2BDXhrjDA0gw%40mail.gmail.com
This commit is contained in:
Daniel Gustafsson 2023-04-07 01:00:21 +02:00
parent a85c60a945
commit 7d71d3dd08
5 changed files with 222 additions and 125 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/access/heap/vacuumlazy.c
View File

@ -389,7 +389,7 @@ heap_vacuum_rel(Relation rel, VacuumParams *params,
Assert(params->index_cleanup != VACOPTVALUE_UNSPECIFIED);
Assert(params->truncate != VACOPTVALUE_UNSPECIFIED &&
params->truncate != VACOPTVALUE_AUTO);
VacuumFailsafeActive = false;
Assert(!VacuumFailsafeActive);
vacrel->consider_bypass_optimization = true;
vacrel->do_index_vacuuming = true;
vacrel->do_index_cleanup = true;

46
src/backend/commands/vacuum.c
View File

@ -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"
@ -523,9 +524,9 @@ vacuum(List *relations, VacuumParams *params, BufferAccessStrategy bstrategy,
{
ListCell *cur;
VacuumUpdateCosts();
in_vacuum = true;
VacuumCostActive = (vacuum_cost_delay > 0);
VacuumFailsafeActive = false;
VacuumUpdateCosts();
VacuumCostBalance = 0;
VacuumPageHit = 0;
VacuumPageMiss = 0;
@ -579,12 +580,20 @@ vacuum(List *relations, VacuumParams *params, BufferAccessStrategy bstrategy,
CommandCounterIncrement();
}
}
/*
* Ensure VacuumFailsafeActive has been reset before vacuuming the
* next relation.
*/
VacuumFailsafeActive = false;
}
}
PG_FINALLY();
{
in_vacuum = false;
VacuumCostActive = false;
VacuumFailsafeActive = false;
VacuumCostBalance = 0;
}
PG_END_TRY();
@ -2245,7 +2254,28 @@ vacuum_delay_point(void)
/* Always check for interrupts */
CHECK_FOR_INTERRUPTS();
if (!VacuumCostActive || InterruptPending)
if (InterruptPending ||
(!VacuumCostActive && !ConfigReloadPending))
return;
/*
* Autovacuum workers should reload the configuration file if requested.
* This allows changes to [autovacuum_]vacuum_cost_limit and
* [autovacuum_]vacuum_cost_delay to take effect while a table is being
* vacuumed or analyzed.
*/
if (ConfigReloadPending && IsAutoVacuumWorkerProcess())
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
VacuumUpdateCosts();
}
/*
* If we disabled cost-based delays after reloading the config file,
* return.
*/
if (!VacuumCostActive)
return;
/*
@ -2278,7 +2308,15 @@ vacuum_delay_point(void)
VacuumCostBalance = 0;
VacuumUpdateCosts();
/*
* Balance and update limit values for autovacuum workers. We must do
* this periodically, as the number of workers across which we are
* balancing the limit may have changed.
*
* TODO: There may be better criteria for determining when to do this
* besides "check after napping".
*/
AutoVacuumUpdateCostLimit();
/* Might have gotten an interrupt while sleeping */
CHECK_FOR_INTERRUPTS();

1
src/backend/commands/vacuumparallel.c
View File

@ -995,7 +995,6 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
false);
/* Set cost-based vacuum delay */
VacuumCostActive = (vacuum_cost_delay > 0);
VacuumUpdateCosts();
VacuumCostBalance = 0;
VacuumPageHit = 0;

297
src/backend/postmaster/autovacuum.c
View File

@ -139,6 +139,18 @@ int Log_autovacuum_min_duration = 600000;
static bool am_autovacuum_launcher = false;
static bool am_autovacuum_worker = false;
/*
* Variables to save the cost-related storage parameters for the current
* relation being vacuumed by this autovacuum worker. Using these, we can
* ensure we don't overwrite the values of vacuum_cost_delay and
* vacuum_cost_limit after reloading the configuration file. They are
* initialized to "invalid" values to indicate that no cost-related storage
* parameters were specified and will be set in do_autovacuum() after checking
* the storage parameters in table_recheck_autovac().
*/
static double av_storage_param_cost_delay = -1;
static int av_storage_param_cost_limit = -1;
/* Flags set by signal handlers */
static volatile sig_atomic_t got_SIGUSR2 = false;
@ -189,8 +201,8 @@ typedef struct autovac_table
{
Oid at_relid;
VacuumParams at_params;
double at_vacuum_cost_delay;
int at_vacuum_cost_limit;
double at_storage_param_vac_cost_delay;
int at_storage_param_vac_cost_limit;
bool at_dobalance;
bool at_sharedrel;
char *at_relname;
@ -209,7 +221,7 @@ 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
@ -223,11 +235,8 @@ typedef struct WorkerInfoData
Oid wi_tableoid;
PGPROC *wi_proc;
TimestampTz wi_launchtime;
bool wi_dobalance;
pg_atomic_flag 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 +282,8 @@ 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_nworkersForBalance 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 +297,7 @@ typedef struct
dlist_head av_runningWorkers;
WorkerInfo av_startingWorker;
AutoVacuumWorkItem av_workItems[NUM_WORKITEMS];
pg_atomic_uint32 av_nworkersForBalance;
} AutoVacuumShmemStruct;
static AutoVacuumShmemStruct *AutoVacuumShmem;
@ -319,7 +331,7 @@ static void launch_worker(TimestampTz now);
static List *get_database_list(void);
static void rebuild_database_list(Oid newdb);
static int db_comparator(const void *a, const void *b);
static void autovac_balance_cost(void);
static void autovac_recalculate_workers_for_balance(void);
static void do_autovacuum(void);
static void FreeWorkerInfo(int code, Datum arg);
@ -669,7 +681,7 @@ AutoVacLauncherMain(int argc, char *argv[])
{
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
AutoVacuumShmem->av_signal[AutoVacRebalance] = false;
autovac_balance_cost();
autovac_recalculate_workers_for_balance();
LWLockRelease(AutovacuumLock);
}
@ -818,11 +830,6 @@ HandleAutoVacLauncherInterrupts(void)
if (!AutoVacuumingActive())
AutoVacLauncherShutdown();
/* rebalance in case the default cost parameters changed */
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
autovac_balance_cost();
LWLockRelease(AutovacuumLock);
/* rebuild the list in case the naptime changed */
rebuild_database_list(InvalidOid);
}
@ -1754,10 +1761,7 @@ FreeWorkerInfo(int code, Datum arg)
MyWorkerInfo->wi_sharedrel = false;
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;
pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance);
dlist_push_head(&AutoVacuumShmem->av_freeWorkers,
&MyWorkerInfo->wi_links);
/* not mine anymore */
@ -1781,10 +1785,20 @@ FreeWorkerInfo(int code, Datum arg)
void
VacuumUpdateCosts(void)
{
double original_cost_delay = vacuum_cost_delay;
int original_cost_limit = vacuum_cost_limit;
if (MyWorkerInfo)
{
vacuum_cost_delay = MyWorkerInfo->wi_cost_delay;
vacuum_cost_limit = MyWorkerInfo->wi_cost_limit;
if (av_storage_param_cost_delay >= 0)
vacuum_cost_delay = av_storage_param_cost_delay;
else if (autovacuum_vac_cost_delay >= 0)
vacuum_cost_delay = autovacuum_vac_cost_delay;
else
/* fall back to VacuumCostDelay */
vacuum_cost_delay = VacuumCostDelay;
AutoVacuumUpdateCostLimit();
}
else
{
@ -1792,88 +1806,128 @@ VacuumUpdateCosts(void)
vacuum_cost_delay = VacuumCostDelay;
vacuum_cost_limit = VacuumCostLimit;
}
/*
* If configuration changes are allowed to impact VacuumCostActive, make
* sure it is updated.
*/
if (VacuumFailsafeActive)
Assert(!VacuumCostActive);
else if (vacuum_cost_delay > 0)
VacuumCostActive = true;
else
{
VacuumCostActive = false;
VacuumCostBalance = 0;
}
if (MyWorkerInfo)
{
Oid dboid,
tableoid;
/* Only log updates to cost-related variables */
if (vacuum_cost_delay == original_cost_delay &&
vacuum_cost_limit == original_cost_limit)
return;
Assert(!LWLockHeldByMe(AutovacuumLock));
LWLockAcquire(AutovacuumLock, LW_SHARED);
dboid = MyWorkerInfo->wi_dboid;
tableoid = MyWorkerInfo->wi_tableoid;
LWLockRelease(AutovacuumLock);
elog(DEBUG2,
"Autovacuum VacuumUpdateCosts(db=%u, rel=%u, dobalance=%s, cost_limit=%d, cost_delay=%g active=%s failsafe=%s)",
dboid, tableoid, pg_atomic_unlocked_test_flag(&MyWorkerInfo->wi_dobalance) ? "no" : "yes",
vacuum_cost_limit, vacuum_cost_delay,
vacuum_cost_delay > 0 ? "yes" : "no",
VacuumFailsafeActive ? "yes" : "no");
}
}
/*
* autovac_balance_cost
* Recalculate the cost limit setting for each active worker.
*
* Caller must hold the AutovacuumLock in exclusive mode.
* Update vacuum_cost_limit 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_nworkersForBalance has been updated by
* another worker or by the autovacuum launcher. They must also call it after a
* config reload.
*/
static void
autovac_balance_cost(void)
void
AutoVacuumUpdateCostLimit(void)
{
if (!MyWorkerInfo)
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;
if (av_storage_param_cost_limit > 0)
vacuum_cost_limit = av_storage_param_cost_limit;
else
{
int nworkers_for_balance;
if (autovacuum_vac_cost_limit > 0)
vacuum_cost_limit = autovacuum_vac_cost_limit;
else
vacuum_cost_limit = VacuumCostLimit;
/* Only balance limit if no cost-related storage parameters specified */
if (pg_atomic_unlocked_test_flag(&MyWorkerInfo->wi_dobalance))
return;
Assert(vacuum_cost_limit > 0);
nworkers_for_balance = pg_atomic_read_u32(&AutoVacuumShmem->av_nworkersForBalance);
/* There is at least 1 autovac worker (this worker) */
if (nworkers_for_balance <= 0)
elog(ERROR, "nworkers_for_balance must be > 0");
vacuum_cost_limit = Max(vacuum_cost_limit / nworkers_for_balance, 1);
}
}
/*
* autovac_recalculate_workers_for_balance
* Recalculate the number of workers to consider, given cost-related
* storage parameters and the current number of active workers.
*
* Caller must hold the AutovacuumLock in at least shared mode to access
* worker->wi_proc.
*/
static void
autovac_recalculate_workers_for_balance(void)
{
dlist_iter iter;
int orig_nworkers_for_balance;
int nworkers_for_balance = 0;
/* not set? nothing to do */
if (vac_cost_limit <= 0 || vac_cost_delay <= 0)
return;
Assert(LWLockHeldByMe(AutovacuumLock));
orig_nworkers_for_balance =
pg_atomic_read_u32(&AutoVacuumShmem->av_nworkersForBalance);
/* 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);
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;
if (worker->wi_proc == NULL ||
pg_atomic_unlocked_test_flag(&worker->wi_dobalance))
continue;
nworkers_for_balance++;
}
/* there are no cost limits -- nothing to do */
if (cost_total <= 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;
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)
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);
}
if (nworkers_for_balance != orig_nworkers_for_balance)
pg_atomic_write_u32(&AutoVacuumShmem->av_nworkersForBalance,
nworkers_for_balance);
}
/*
@ -2421,23 +2475,34 @@ do_autovacuum(void)
continue;
}
/* Must hold AutovacuumLock while mucking with cost balance info */
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
/*
* Save the cost-related storage parameter values in global variables
* for reference when updating vacuum_cost_delay and vacuum_cost_limit
* during vacuuming this table.
*/
av_storage_param_cost_delay = tab->at_storage_param_vac_cost_delay;
av_storage_param_cost_limit = tab->at_storage_param_vac_cost_limit;
/* 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;
/*
* We only expect this worker to ever set the flag, so don't bother
* checking the return value. We shouldn't have to retry.
*/
if (tab->at_dobalance)
pg_atomic_test_set_flag(&MyWorkerInfo->wi_dobalance);
else
pg_atomic_clear_flag(&MyWorkerInfo->wi_dobalance);
/* do a balance */
autovac_balance_cost();
LWLockAcquire(AutovacuumLock, LW_SHARED);
autovac_recalculate_workers_for_balance();
LWLockRelease(AutovacuumLock);
/* set the active cost parameters from the result of that */
/*
* We wait until this point to update cost delay and cost limit
* values, even though we reloaded the configuration file above, so
* that we can take into account the cost-related storage parameters.
*/
VacuumUpdateCosts();
/* done */
LWLockRelease(AutovacuumLock);
/* clean up memory before each iteration */
MemoryContextResetAndDeleteChildren(PortalContext);
@ -2521,16 +2586,17 @@ deleted:
pfree(tab);
/*
* 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.
* Remove my info from shared memory. We set wi_dobalance on the
* assumption that we are more likely than not to vacuum a table with
* no cost-related storage parameters next, so we want to claim our
* share of I/O as soon as possible to avoid thrashing the global
* balance.
*/
LWLockAcquire(AutovacuumScheduleLock, LW_EXCLUSIVE);
MyWorkerInfo->wi_tableoid = InvalidOid;
MyWorkerInfo->wi_sharedrel = false;
LWLockRelease(AutovacuumScheduleLock);
pg_atomic_test_set_flag(&MyWorkerInfo->wi_dobalance);
}
/*
@ -2562,6 +2628,7 @@ deleted:
{
ConfigReloadPending = false;
ProcessConfigFile(PGC_SIGHUP);
VacuumUpdateCosts();
}
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
@ -2797,8 +2864,6 @@ 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;
/*
@ -2808,20 +2873,6 @@ 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
@ -2877,8 +2928,10 @@ 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_storage_param_vac_cost_limit = avopts ?
avopts->vacuum_cost_limit : 0;
tab->at_storage_param_vac_cost_delay = avopts ?
avopts->vacuum_cost_delay : -1;
tab->at_relname = NULL;
tab->at_nspname = NULL;
tab->at_datname = NULL;
@ -3382,8 +3435,14 @@ AutoVacuumShmemInit(void)
/* 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_flag(&worker[i].wi_dobalance);
}
pg_atomic_init_u32(&AutoVacuumShmem->av_nworkersForBalance, 0);
}
else
Assert(found);

1
src/include/commands/vacuum.h
View File

@ -350,6 +350,7 @@ extern IndexBulkDeleteResult *vac_cleanup_one_index(IndexVacuumInfo *ivinfo,
extern Size vac_max_items_to_alloc_size(int max_items);
/* In postmaster/autovacuum.c */
extern void AutoVacuumUpdateCostLimit(void);
extern void VacuumUpdateCosts(void);
/* in commands/vacuumparallel.c */