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Date: Tue, 2 Feb 2010 13:25:28 -0700
Message-ID: <dcc563d11002021225v757f48c8i9faee286f82f703f@mail.gmail.com>
Subject: Re: System overload / context switching / oom, 8.3
From: Scott Marlowe <scott.marlowe@gmail.com>
To: Rob <rclemley@yahoo.com>
Cc: pgsql-performance@postgresql.org
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On Tue, Feb 2, 2010 at 12:11 PM, Rob <rclemley@yahoo.com> wrote:
> pg 8.3.9, Debian Etch, 8gb ram, quadcore xeon, megaraid (more details at =
end)
> ~240 active databases, 800+ db connections via tcp.
>
> Everything goes along fairly well, load average from 0.5 to 4.0. =A0Disk
> IO is writing about 12-20 MB every 4 or 5 seconds. =A0Cache memory about
> 4gb. =A0Then under load, we see swapping and then context switch storm an=
d
> then oom-killer.

SNIP

> postgresql.conf:
> max_connections =3D 1100
> work_mem =3D 32MB

32MB * 1000 =3D 32,000MB...  And that's if you max out connections and
they each only do 1 sort.  If you're running many queries that run > 1
sorts it'll happen a lot sooner.

Either drop max connections or work_mem is what I'd do to start with.
If you have one or two reporting apps that need it higher, then set it
higher for just those connections / users.