Re: Shared Memory Sizing

From: Curt Sampson <cjs(at)cynic(dot)net>
To: Andrew Sullivan <andrew(at)libertyrms(dot)info>
Cc: Pg-General <pgsql-general(at)postgresql(dot)org>
Subject: Re: Shared Memory Sizing
Date: 2002-06-28 10:16:08
Message-ID: Pine.NEB.4.43.0206281914000.6613-100000@angelic.cynic.net
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On Thu, 27 Jun 2002, Andrew Sullivan wrote:

> Consider all the other things you're doing on the machine -- just
> little things, like cron and such. All that takes memory.
> Therefore, it's dangerous not to let the OS manage a good chunk of
> memory.

Postgres itself doesn't manage all of its own memory usage. Sorts
and things, for example, are allocated from OS-owned memory, not
postgres' shared memory. So if you give most of the machine memory
over to postgres shared buffers, postgres itself might drive the
machine into swapping because it's got memory that should be used
for the sort, but can't be. That's why it's better to move to
minimum shared memory rather than maximum.

cjs
--
Curt Sampson <cjs(at)cynic(dot)net> +81 90 7737 2974 http://www.netbsd.org
Don't you know, in this new Dark Age, we're all light. --XTC

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