Re: [HACKERS] Automatically setting work_mem

From: Bruno Wolff III <bruno(at)wolff(dot)to>
To: daveg <daveg(at)sonic(dot)net>
Cc: David Fetter <david(at)fetter(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Luke Lonergan <llonergan(at)greenplum(dot)com>, pgsql-patches(at)postgresql(dot)org, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Automatically setting work_mem
Date: 2006-04-23 15:08:01
Message-ID: 20060423150801.GA31650@wolff.to
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On Sat, Apr 22, 2006 at 14:20:32 -0700,
daveg <daveg(at)sonic(dot)net> wrote:
> On Sat, Apr 22, 2006 at 01:49:25PM -0700, David Fetter wrote:
> > On Sat, Apr 22, 2006 at 01:14:42PM -0700, David Gould wrote:
> >
> > > To avoid running out of swap and triggering the oom killer we have
> > > had to reduce work_mem below what we prefer.
> >
> > Dunno about your work_mem, but you can make sure the OOM killer
> > doesn't kill you as follows <http://lwn.net/Articles/104185/>.
>
> Or I could run with overcommit turned off, but we like overcommit because
> things like vaccuum appear to allocate maint_work_mem when they start, so
> if that is set at say 100 Mb it will allocate 100 Mb even to vacuum a 2
> page table. Overcommit lets this sort of thing get by without createing
> a need for even more swap.

I would expect that you would still come out ahead commiting some disk
space to swap, that will probably never be used, that allows you to better
configure your memory usage.

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