Re: Performance problems on 4/8way Opteron (dualcore)

On 7/29/05 10:46 AM, "Josh Berkus" <josh(at)agliodbs(dot)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