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Re: hyperthreaded cpu still an issue in 8.4?

From: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
To: Doug Hunley <doug(at)hunley(dot)homeip(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: hyperthreaded cpu still an issue in 8.4?
Date: 2009-07-21 14:16:32
Message-ID: dcc563d10907210716m22651d8dvfcd331c0d8f6ea8b@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, Jul 21, 2009 at 6:42 AM, Doug Hunley<doug(at)hunley(dot)homeip(dot)net> wrote:
> Just wondering is the issue referenced in
> http://archives.postgresql.org/pgsql-performance/2005-11/msg00415.php
> is still present in 8.4 or if some tunable (or other) made the use of
> hyperthreading a non-issue. We're looking to upgrade our servers soon
> for performance reasons and am trying to determine if more cpus (no
> HT) or less cpus (with HT) are the way to go. Thx

This isn't really an application tunable so much as a kernel level
tunable.  PostgreSQL seems to have scaled pretty well a couple years
ago in the tweakers.net benchmark of the Sun T1 CPU with 4 threads per
core.  However, at the time 4 AMD cores were spanking 8 Sun T1 cores
with 4 threads each.

Now, whether or not their benchmark applies to your application only
you can say.  Can you get machines on a 30 day trial program to
benchmark them and decide which to go with?  I'm guessing that dual
6core Opterons with lots of memory is the current king of the hill for
reasonably priced pg servers that are running CPU bound loads.

If you're mostly IO bound then it really doesn't matter which CPU.

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Subject: Re: hyperthreaded cpu still an issue in 8.4?
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