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Re: Problem with 8.4 stats collector high load

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Jakub Ouhrabka <kuba(at)comgate(dot)cz>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Problem with 8.4 stats collector high load
Date: 2010-02-16 14:10:50
Message-ID: 20100216141050.GB5330@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-hackers
Jakub Ouhrabka wrote:
> > You might want to try setting log_autovacuum_min_duration=0 in the
> > postgresql.conf
> 
> Thanks, tried it. There is nothing in the log - the actual
> vacuum/analyze commands are not run (as there is no query activity).
> I suspect that autovacuum is checking each database if it should run
> - and decides not to run. See the randomly catch process in ps
> output/pg_stat_activity mentioned in earlier mail. I suspect that
> this checking generates the load. Is it possible?

Yes.  There were some changes that needed to be done to autovacuum so
that it didn't read the stats file too often, but I don't recall if I
got around to it.

Note that autovacuum_naptime=1min (default value) means that it's
checking stats 650 times per minute (there's a throttle IIRC but still).
Maybe you should decrease naptime a bit.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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