[Beowulf] Re: Opteron 275 performance

[Joe Landman]

Hi Steve:

   Not knowing the details of your calculations might be an issue, but 
you can read about our experiences with a number of chemistry and 
informatics codes on dual core Opteron systems.  See 
http://enterprise2.amd.com/downloadables/Dual_Core_Performance.pdf for 
more details.

Joe

Steve Cousins wrote:
> On Thu, 14 Jul 2005 11:25:12 +0100 Igor Kozin wrote:
> 
> 
>> But now for 4cores/2CPUs per Opteron node to force the using of
>>
>>>only 2 cores (from 4), by 1 for each chip, we'll need to have
>>>cpu affinity support in Linux.
>>
>>Mikhail,
>>you can use "taskset" for that purpose. 
>>For example, (perhaps not in the most elegant form)
>>        mpiexec  -n 1 taskset -c 0 $code : -n 1 taskset -c 2 $code
>>But I doubt you want to let the idle cores to do something else 
>>in the mean time. However small you will generally see an increase 
>>in performance if you use all the cores.
> 
> 
> We are considering getting a Dual Dual-Core Opteron system vs. two Dual
> Opteron systems.  We like the ability to use all four cores on one model
> but a lot of what we'll do is have two models running at the same time,
> each using two cores.  
> 
> We are worried that running two models on one system with four cores (each
> model using two cores) will not work as well as using two systems, each
> with two cores/cpu's.  Is this what you were refering to (Igor) when you
> wrote:
> 
> 
>>But I doubt you want to let the idle cores to do something else
>>in the mean time. 
> 
> 
> We have an 8 CPU SGI Origin 3200 that has no problem doing this sort of
> thing.  I'm just curious what the implications are of doing this with the
> Dual Core Opteron cpu's.  
> 
> Thanks,
> 
> Steve 
> ______________________________________________________________________
>  Steve Cousins, Ocean Modeling Group    Email: cousins at umit.maine.edu
>  Marine Sciences, 208 Libby Hall        http://rocky.umeoce.maine.edu
>  Univ. of Maine, Orono, ME 04469        Phone: (207) 581-4302
> 
> 
> 
> 
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-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax  : +1 734 786 8452
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