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Re: hyperthreaded cpu still an issue in 8.4?

From: Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com>
To: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
Cc: Doug Hunley <doug(at)hunley(dot)homeip(dot)net>, pgsql-performance(at)postgresql(dot)org
Subject: Re: hyperthreaded cpu still an issue in 8.4?
Date: 2009-07-21 14:36:11
Message-ID: 2f4958ff0907210736h72e70101nb63b2da091104d8f@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, Jul 21, 2009 at 3:16 PM, Scott Marlowe<scott(dot)marlowe(at)gmail(dot)com> wrote:
> 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.
Unless he is doing a lot of computations, on small sets of data.


Now I am confused, HT is not anywhere near what 'threads' are on sparcs afaik.



-- 
GJ

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