User-Agent: Microsoft-Entourage/11.1.0.040913
Date: Fri, 29 Jul 2005 12:21:53 -0700
Subject: Re: Performance problems on 4/8way Opteron (dualcore)
From: "J. Andrew Rogers" <jrogers@neopolitan.com>
To: <josh@agliodbs.com>, <pgsql-performance@postgresql.org>
Cc: Dirk Lutzeb=?ISO-8859-1?B?5A==?=ck <lutzeb@aeccom.com>,
	Sven Geisler <sgeisler@aeccom.com>
Message-ID: <BF0FCFE1.71F%jrogers@neopolitan.com>
In-Reply-To: <200507291046.10318.josh@agliodbs.com>
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On 7/29/05 10:46 AM, "Josh Berkus" <josh@agliodbs.com> wrote:
>> does anybody have expierence with this machine (4x 875 dual core Opteron
>> CPUs)?
> 
> Nope.   I suspect that you may be the first person to report in on
> dual-cores.  There may be special compile issues with dual-cores that
> we've not yet encountered.


There was recently a discussion of similar types of problems on a couple of
the supercomputing lists, regarding surprisingly substandard performance
from large dual-core opteron installations.

The problem as I remember it boiled down to the Linux kernel handling
memory/process management very badly on large dual core systems --
pathological NUMA behavior.  However, this problem has apparently been fixed
in Linux v2.6.12+, and using the more recent kernel on large dual core
systems generated *massive* performance improvements on these systems for
the individuals with this issue.  Using the patched kernel, one gets the
performance most people were expecting.

The v2.6.12+ kernels are a bit new, but they contain a very important
performance patch for systems like the one above.  It would definitely be
worth testing if possible.


J. Andrew Rogers