[Beowulf] VMC - Virtual Machine Console

stephen mulcahy smulcahy at aplpi.com
Fri Jan 18 03:57:45 EST 2008


Shannon V. Davidson wrote:
> 
> Michael H. Frese wrote:
>> At 08:31 AM 1/16/2008, Jeffrey B. Layton wrote:
>>> - With multi-core processors, to get the best performance you want to
>>>   assign a process to a core.
>>
>> Excuse my ignorance, please, but can someone tell me how to do that on 
>> Linux (2.6 kernels would be fine)?
> 
> sched_setaffinity(2)
> taskset(1)
> numactl(1)

Hi,

As an aside to this, do 2.6 kernels make some efforts to keep a process 
on a specific core anyways recognising the benefits to the cache of 
doing so (I suspect they do but maybe I just dreamed it up)?

As a further aside, some MPI libraries (OpenMPI comes to mind) seem to 
make some efforts to keep processes on the same cores also (or can be 
instructed to via a run-time option).

I'm wondering how much of a performance benefit there is to using the 
above-mentioned OS commands to set affinity (versus the trade-off in 
setting this up).

-stephen

-- 
Stephen Mulcahy, Applepie Solutions Ltd., Innovation in Business Center,
GMIT, Dublin Rd, Galway, Ireland.  +353.91.751262  http://www.aplpi.com
Registered in Ireland, no. 289353 (5 Woodlands Avenue, Renmore, Galway)
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