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Dynamically set a lower bound on autovacuum nap time so that we don't rebuild 

the database list too often.

Per bug report from Łukasz Jagiełło and ensuing discussion on
pgsql-performance.
This commit is contained in:
Alvaro Herrera 2009-06-09 16:41:02 +00:00
parent e5de601267
commit e8f28cb25d
1 changed files with 16 additions and 5 deletions
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21
src/backend/postmaster/autovacuum.c
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@ -55,7 +55,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.95 2009/05/15 15:56:39 tgl Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.96 2009/06/09 16:41:02 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@ -123,6 +123,8 @@ int Log_autovacuum_min_duration = -1;
/* how long to keep pgstat data in the launcher, in milliseconds */
#define STATS_READ_DELAY 1000
/* the minimum allowed time between two awakening of the launcher */
#define MIN_AUTOVAC_SLEEPTIME 100.0 /* milliseconds */
/* Flags to tell if we are in an autovacuum process */
static bool am_autovacuum_launcher = false;
@ -822,11 +824,11 @@ launcher_determine_sleep(bool canlaunch, bool recursing, struct timeval * nap)
return;
}
/* 100ms is the smallest time we'll allow the launcher to sleep */
if (nap->tv_sec <= 0 && nap->tv_usec <= 100000)
/* The smallest time we'll allow the launcher to sleep. */
if (nap->tv_sec <= 0 && nap->tv_usec <= MIN_AUTOVAC_SLEEPTIME * 1000)
{
nap->tv_sec = 0;
nap->tv_usec = 100000; /* 100 ms */
nap->tv_usec = MIN_AUTOVAC_SLEEPTIME * 1000;
}
}
@ -997,8 +999,17 @@ rebuild_database_list(Oid newdb)
/* sort the array */
qsort(dbary, nelems, sizeof(avl_dbase), db_comparator);
/* this is the time interval between databases in the schedule */
/*
* Determine the time interval between databases in the schedule.
* If we see that the configured naptime would take us to sleep times
* lower than our min sleep time (which launcher_determine_sleep is
* coded not to allow), silently use a larger naptime (but don't touch
* the GUC variable).
*/
millis_increment = 1000.0 * autovacuum_naptime / nelems;
if (millis_increment <= MIN_AUTOVAC_SLEEPTIME)
millis_increment = MIN_AUTOVAC_SLEEPTIME * 1.1;
current_time = GetCurrentTimestamp();
/*