[Rd] Some timings for 64 bit Opteron (ATLAS, GOTO, std)

A.J. Rossini rossini at blindglobe.net
Tue Mar 2 18:20:01 MET 2004

And my understanding is completely imperfect, but note that
organization (and selection) of memory modules on the motherboard can
be critical for speed with the opterons; well known issue on the
beowulf lists.


Peter Dalgaard <p.dalgaard at biostat.ku.dk> writes:

> "Liaw, Andy" <andy_liaw at merck.com> writes:
>> Hi Martin,
>> When I attended the LinuxWorld Expo in NYC back in January, I chatted with
>> some folks at the AMD booth, as well as guys from Penguin Computing (where
>> we bought our Opteron box).  I was told that the Operton has this somewhat
>> strange setup that the memory is controlled by one CPU.  The net effect of
>> this being that when both CPUs are running, one might only be running at
>> around 90% instead of 99%.  The `NUMA' kernel is supposed to fix this
>> problem.  I wonder if this is related to the performance of the threaded
>> GOTO lib that you saw.  Has anyone tried the NUMA kernel?
>> Best,
>> Andy
> My understanding is slightly different (I could be wrong though, I'm
> hardly a hardware engineer): Each CPU controls one block of memory,
> and only some motherboard have memory slots for both CPUs. If CPU2
> wants to talk to CPU1's memory it has to ask CPU1 for it, with the
> obvious potential for a performance hit.
> I'll see if I can get around to redoing my Opteron builds and trying
> Martin's benchmarks in the next couple of days.
>         -p
> -- 
>    O__  ---- Peter Dalgaard             Blegdamsvej 3  
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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