Date: Tue, 13 Jun 2006 18:17:30 -0500
From: "Jim C. Nasby" <jnasby@pervasive.com>
To: Mischa Sandberg <mischa@ca.sophos.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Solaris shared_buffers anomaly?
Message-ID: <20060613231730.GS34196@pervasive.com>
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	<20060613200810.GZ34196@pervasive.com>
	<448F3A6E.6080908@ca.sophos.com>
	<20060613224759.GM34196@pervasive.com>
	<448F4842.4010305@ca.sophos.com>
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On Tue, Jun 13, 2006 at 04:20:34PM -0700, Mischa Sandberg wrote:
> Jim C. Nasby wrote:
> >On Tue, Jun 13, 2006 at 03:21:34PM -0700, Mischa Sandberg wrote:
> >>Raised shared_buffers to 16000 (128MB).
> >>DB server dropped to a CRAWL.
> >>
> >>vmstat showed that it was swapping like crazy.
> >>Dropped shared_buffers back down again. 
> >>Swapping stopped.
> >
> >What's sort_mem set to? I suspect you simply ran the machine out of
> >memory.
> 
> 8192 (8MB). No issue when shared_buffers was 2000; same apps always.
 
So if all 50 backends were running a sort, you'd use 400MB. The box has
4G, right?

> >Also, Solaris by default will only use a portion of memory for
> >filesystem caching, which will kill PostgreSQL performance.
> 
> Yep, tested /etc/system segmap_percent at 20,40,60. 
> No significant difference between 20 and 60.

That's pretty disturbing... how large is your database?
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461