From: Josh Berkus <josh@agliodbs.com>
To: Cédric Villemain <cedric.villemain.debian@gmail.com>
Cc: jd@commandprompt.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Write-heavy pg_stats_collector on mostly idle server
Date: Mon, 07 Feb 2011 17:39:45 -0800
Message-ID: <4D509EE1.4070305@agliodbs.com> (raw)
In-Reply-To: <AANLkTin5T+KartVKBjYRJuCNDEcTUAJkMW6Zna6uJi1Q@mail.gmail.com>
References: <4D4C4E15.20401@agliodbs.com>
<AANLkTinpWWrDHR9KJNebgtbvpXpL4UdQszD0GxF+FWWu@mail.gmail.com>
<4D507920.2030909@agliodbs.com>
<1297120356.18411.197.camel@jd-desktop>
<AANLkTin5T+KartVKBjYRJuCNDEcTUAJkMW6Zna6uJi1Q@mail.gmail.com>
> Ooops.
> It looks like you are right, see ./src/backend/postmaster/pgstat.c
>
> 3c2313f4 (Tom Lane 2008-11-03 01:17:08 +0000 2926)
> if (last_statwrite < last_statrequest)
> 70d75697 (Magnus Hagander 2008-08-05 12:09:30 +0000 2927)
> pgstat_write_statsfile(false);
This is a different issue. This is happening because we have a bunch of
databases (25 to 35) and as a result autovacuum is requesting the stats
file rather frequently. And autovacuum for whatever reason won't accept
a stats file more than 10ms old, so it pretty much rewrites the stats
file on every request.
At least, that's my reading of it after poking around and talking to
Gierth.
It seems like that 10ms window for autovac is way too small.
--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: josh@agliodbs.com, cedric.villemain.debian@gmail.com, jd@commandprompt.com
Subject: Re: Write-heavy pg_stats_collector on mostly idle server
In-Reply-To: <4D509EE1.4070305@agliodbs.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox