To: Josh Kupershmidt <schmiddy@gmail.com>
cc: Greg Smith <greg@2ndquadrant.com>, Chris <lists@deksai.com>,
	pgsql-performance@postgresql.org
Subject: Re: stats collector suddenly causing lots of IO 
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Comments: In-reply-to Josh Kupershmidt <schmiddy@gmail.com>
	message dated "Fri, 16 Apr 2010 14:35:56 -0400"
Date: Fri, 16 Apr 2010 15:22:42 -0400
Message-ID: <13663.1271445762@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Josh Kupershmidt <schmiddy@gmail.com> writes:
>         name         | current_setting |       source
> ----------------------+-----------------+--------------------
>  vacuum_cost_delay    | 200ms           | configuration file
>  vacuum_cost_limit    | 100             | configuration file
>  vacuum_cost_page_hit | 6               | configuration file
> 
> It looks like the default which I have of autovacuum_vacuum_cost_limit
> = -1, which means it's inheriting the vacuum_cost_limit of 100 I had
> set. I'll try bumping vacuum_cost_limit up to 1000 or so.

Actually I think the main problem is that cost_delay value, which is
probably an order of magnitude too high.  The way to limit vacuum's
I/O impact on other stuff is to make it take frequent short delays,
not have it run full speed and then sleep a long time.  In any case,
your current settings have got it sleeping way too much.  Two WEEKS !!!??

			regards, tom lane