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Separate vacuum cost variables from GUCs 

Vacuum code run both by autovacuum workers and a backend doing
VACUUM/ANALYZE previously inspected VacuumCostLimit and VacuumCostDelay,
which are the global variables backing the GUCs vacuum_cost_limit and
vacuum_cost_delay.

Autovacuum workers needed to override these variables with their
own values, derived from autovacuum_vacuum_cost_limit and
autovacuum_vacuum_cost_delay and worker cost limit balancing logic.
This led to confusing code which, in some cases, both derived and
set a new value of VacuumCostLimit from VacuumCostLimit.

In preparation for refreshing these GUC values more often, introduce
new, independent global variables and add a function to update them
using the GUCs and existing logic.

Per suggestion by Kyotaro Horiguchi

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 00:54:53 +02:00
parent 71a825194f
commit a85c60a945
5 changed files with 40 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/backend/commands/vacuum.c
View File

@ -72,6 +72,15 @@ int vacuum_multixact_freeze_table_age;
int vacuum_failsafe_age;
int vacuum_multixact_failsafe_age;
/*
* Variables for cost-based vacuum delay. The defaults differ between
* autovacuum and vacuum. They should be set with the appropriate GUC value in
* vacuum code. They are initialized here to the defaults for client backends
* executing VACUUM or ANALYZE.
*/
double vacuum_cost_delay = 0;
int vacuum_cost_limit = 200;
/*
* VacuumFailsafeActive is a defined as a global so that we can determine
* whether or not to re-enable cost-based vacuum delay when vacuuming a table.
@ -514,8 +523,9 @@ vacuum(List *relations, VacuumParams *params, BufferAccessStrategy bstrategy,
{
ListCell *cur;
VacuumUpdateCosts();
in_vacuum = true;
VacuumCostActive = (VacuumCostDelay > 0);
VacuumCostActive = (vacuum_cost_delay > 0);
VacuumCostBalance = 0;
VacuumPageHit = 0;
VacuumPageMiss = 0;
@ -2244,14 +2254,14 @@ vacuum_delay_point(void)
*/
if (VacuumSharedCostBalance != NULL)
msec = compute_parallel_delay();
else if (VacuumCostBalance >= VacuumCostLimit)
msec = VacuumCostDelay * VacuumCostBalance / VacuumCostLimit;
else if (VacuumCostBalance >= vacuum_cost_limit)
msec = vacuum_cost_delay * VacuumCostBalance / vacuum_cost_limit;
/* Nap if appropriate */
if (msec > 0)
{
if (msec > VacuumCostDelay * 4)
msec = VacuumCostDelay * 4;
if (msec > vacuum_cost_delay * 4)
msec = vacuum_cost_delay * 4;
pgstat_report_wait_start(WAIT_EVENT_VACUUM_DELAY);
pg_usleep(msec * 1000);
@ -2268,8 +2278,7 @@ vacuum_delay_point(void)
VacuumCostBalance = 0;
/* update balance values for workers */
AutoVacuumUpdateDelay();
VacuumUpdateCosts();
/* Might have gotten an interrupt while sleeping */
CHECK_FOR_INTERRUPTS();
@ -2319,11 +2328,11 @@ compute_parallel_delay(void)
/* Compute the total local balance for the current worker */
VacuumCostBalanceLocal += VacuumCostBalance;
if ((shared_balance >= VacuumCostLimit) &&
(VacuumCostBalanceLocal > 0.5 * ((double) VacuumCostLimit / nworkers)))
if ((shared_balance >= vacuum_cost_limit) &&
(VacuumCostBalanceLocal > 0.5 * ((double) vacuum_cost_limit / nworkers)))
{
/* Compute sleep time based on the local cost balance */
msec = VacuumCostDelay * VacuumCostBalanceLocal / VacuumCostLimit;
msec = vacuum_cost_delay * VacuumCostBalanceLocal / vacuum_cost_limit;
pg_atomic_sub_fetch_u32(VacuumSharedCostBalance, VacuumCostBalanceLocal);
VacuumCostBalanceLocal = 0;
}

3
src/backend/commands/vacuumparallel.c
View File

@ -995,7 +995,8 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
false);
/* Set cost-based vacuum delay */
VacuumCostActive = (VacuumCostDelay > 0);
VacuumCostActive = (vacuum_cost_delay > 0);
VacuumUpdateCosts();
VacuumCostBalance = 0;
VacuumPageHit = 0;
VacuumPageMiss = 0;

34
src/backend/postmaster/autovacuum.c
View File

@ -1773,16 +1773,24 @@ 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 vacuum cost-based delay-related parameters for autovacuum workers and
* backends executing VACUUM or ANALYZE using the value of relevant GUCs and
* global state. This must be called during setup for vacuum and after every
* config reload to ensure up-to-date values.
*/
void
AutoVacuumUpdateDelay(void)
VacuumUpdateCosts(void)
{
if (MyWorkerInfo)
{
VacuumCostDelay = MyWorkerInfo->wi_cost_delay;
VacuumCostLimit = MyWorkerInfo->wi_cost_limit;
vacuum_cost_delay = MyWorkerInfo->wi_cost_delay;
vacuum_cost_limit = MyWorkerInfo->wi_cost_limit;
}
else
{
/* Must be explicit VACUUM or ANALYZE */
vacuum_cost_delay = VacuumCostDelay;
vacuum_cost_limit = VacuumCostLimit;
}
}
@ -2311,8 +2319,6 @@ do_autovacuum(void)
autovac_table *tab;
bool isshared;
bool skipit;
double stdVacuumCostDelay;
int stdVacuumCostLimit;
dlist_iter iter;
CHECK_FOR_INTERRUPTS();
@ -2415,14 +2421,6 @@ 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;
/* Must hold AutovacuumLock while mucking with cost balance info */
LWLockAcquire(AutovacuumLock, LW_EXCLUSIVE);
@ -2436,7 +2434,7 @@ do_autovacuum(void)
autovac_balance_cost();
/* set the active cost parameters from the result of that */
AutoVacuumUpdateDelay();
VacuumUpdateCosts();
/* done */
LWLockRelease(AutovacuumLock);
@ -2533,10 +2531,6 @@ deleted:
MyWorkerInfo->wi_tableoid = InvalidOid;
MyWorkerInfo->wi_sharedrel = false;
LWLockRelease(AutovacuumScheduleLock);
/* restore vacuum cost GUCs for the next iteration */
VacuumCostDelay = stdVacuumCostDelay;
VacuumCostLimit = stdVacuumCostLimit;
}
/*

5
src/include/commands/vacuum.h
View File

@ -307,6 +307,8 @@ extern PGDLLIMPORT pg_atomic_uint32 *VacuumActiveNWorkers;
extern PGDLLIMPORT int VacuumCostBalanceLocal;
extern PGDLLIMPORT bool VacuumFailsafeActive;
extern PGDLLIMPORT double vacuum_cost_delay;
extern PGDLLIMPORT int vacuum_cost_limit;
/* in commands/vacuum.c */
extern void ExecVacuum(ParseState *pstate, VacuumStmt *vacstmt, bool isTopLevel);
@ -347,6 +349,9 @@ extern IndexBulkDeleteResult *vac_cleanup_one_index(IndexVacuumInfo *ivinfo,
IndexBulkDeleteResult *istat);
extern Size vac_max_items_to_alloc_size(int max_items);
/* In postmaster/autovacuum.c */
extern void VacuumUpdateCosts(void);
/* in commands/vacuumparallel.c */
extern ParallelVacuumState *parallel_vacuum_init(Relation rel, Relation *indrels,
int nindexes, int nrequested_workers,

3
src/include/postmaster/autovacuum.h
View File

@ -63,9 +63,6 @@ extern int StartAutoVacWorker(void);
/* called from postmaster when a worker could not be forked */
extern void AutoVacWorkerFailed(void);
/* autovacuum cost-delay balancer */
extern void AutoVacuumUpdateDelay(void);
#ifdef EXEC_BACKEND
extern void AutoVacLauncherMain(int argc, char *argv[]) pg_attribute_noreturn();
extern void AutoVacWorkerMain(int argc, char *argv[]) pg_attribute_noreturn();