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

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