Re: postgres 7.4 at 100%

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Frank Knobbe <frank(at)knobbe(dot)us>
Cc: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org
Subject: Re: postgres 7.4 at 100%
Date: 2004-06-28 05:19:42
Message-ID: 17884.1088399982@sss.pgh.pa.us
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Frank Knobbe <frank(at)knobbe(dot)us> writes:
> On Sun, 2004-06-27 at 00:33, Christopher Kings-Lynne wrote:
>>> I upped effective_cache to 16000 KB and I could only up the
>>> shared_buffers to 3000. Anything more and postgres would not start.

>> You need to greatly incrase the shared memory max setting on your
>> machine so that you can use at the very least, 10000 shared buffers.

> Doug said the same, yet the PG Tuning article recommends not make this
> too large as it is just temporary used by the query queue or so.

The original report was that the guy had it set to 40 (!?), which is
clearly far below the minimum reasonable value. But I'd not expect a
huge difference between 3000 and 10000 --- in my experience, 1000 is
enough to get you over the "knee" of the performance curve and into
the domain of marginal improvements.

So while he surely should not go back to 40, it seems there's another
factor involved here that we've not recognized yet.

regards, tom lane

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