Content-Type: text/plain; charset=UTF-8
Cc: Jesper Krogh <jesper@krogh.cc>,
	pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Aggressive autovacuuming ?
From: Alvaro Herrera <alvherre@commandprompt.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
In-reply-to: <AANLkTilXSrrBTDOs6JO4iD9gPNbj6Z-RMdraaanbEEg7@mail.gmail.com>
References: <4C1E537D.5030904@krogh.cc>
	<AANLkTilXSrrBTDOs6JO4iD9gPNbj6Z-RMdraaanbEEg7@mail.gmail.com>
Date: Mon, 21 Jun 2010 12:36:54 -0400
Message-Id: <1277137973-sup-953@alvh.no-ip.org>
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Excerpts from Scott Marlowe's message of dom jun 20 16:13:15 -0400 2010:
> On Sun, Jun 20, 2010 at 11:44 AM, Jesper Krogh <jesper@krogh.cc> wrote:
> > Hi.
> >
> > I have been wondering if anyone has been experimenting with "really
> > agressive"
> > autovacuuming.
> 
> I have been using moderately aggressive autovac, with 6 or more
> threads running with 1ms sleep, then keeping track of them to see if
> they're being too aggresive.  Basically as long as io utilization
> doesn't hit 100% it doesn't seem to have any negative or even
> noticeable effect.

Keep in mind that autovacuum scales down the cost limit the more workers
there are.  So if you have 10ms sleeps and 1 worker, it should roughly
use a similar amount of I/O than if you have 10ms sleeps and 10 workers
(each worker would sleep 10 times more frequently).

-- 
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support