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Subject: Re: [OMPI users] Memory affinity
From: Tim Prince (n8tm_at_[hidden])
Date: 2010-09-27 16:52:03


  On 9/27/2010 12:21 PM, Gabriele Fatigati wrote:
> HI Tim,
>
> I have read that link, but I haven't understood if enabling processor
> affinity are enabled also memory affinity because is written that:
>
> "Note that memory affinity support is enabled only when processor
> affinity is enabled"
>
> Can i set processory affinity without memory affinity? This is my question..
>
>
> 2010/9/27 Tim Prince<n8tm_at_[hidden]>
>> On 9/27/2010 9:01 AM, Gabriele Fatigati wrote:
>>> if OpenMPI is numa-compiled, memory affinity is enabled by default? Because I didn't find memory affinity alone ( similar) parameter to set at 1.
>>>
>>>
>> The FAQ http://www.open-mpi.org/faq/?category=tuning#using-paffinity has a useful introduction to affinity. It's available in a default build, but not enabled by default.
>>
Memory affinity is implied by processor affinity. Your system libraries
are set up so as to cause any memory allocated to be made local to the
processor, if possible. That's one of the primary benefits of processor
affinity. Not being an expert in openmpi, I assume, in the absence of
further easily accessible documentation, there's no useful explicit way
to disable maffinity while using paffinity on platforms other than the
specified legacy platforms.

-- 
Tim Prince