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Subject: Re: [OMPI users] Hybrid program
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-12-02 20:56:54


Fair enough; let me know what you find. It would be good to
understand exactly why you're seeing what you're seeing...

On Dec 2, 2008, at 5:47 PM, Edgar Gabriel wrote:

> its on OpenSuSE 11 with kernel 2.6.25.11. I don't know the libnuma
> library version, but I suspect that its fairly new.
>
> I will try to investigate that in the next days a little more. I do
> think that they use sched_setaffinity() underneath the hood (because
> in one of my failed attempts when I passed in the wrong argument, I
> got actually the same error message that I got earlier with
> sched_setaffinity), but they must do something additionally
> underneath.
>
> Anyway, I just wanted to report the result, and that there is
> obviously a difference, even if can't explain it right now in details.
>
> Thanks
> Edgar
>
> Jeff Squyres wrote:
>> On Dec 2, 2008, at 11:27 AM, Edgar Gabriel wrote:
>>> so I ran a couple of tests today and I can not confirm your
>>> statement. I wrote simple a simple test code where a process first
>>> sets an affinity mask and than spawns a number of threads. The
>>> threads modify the affinity mask and every thread ( including the
>>> master thread) print out there affinity mask at the end.
>>>
>>> With sched_getaffinity() and sched_setaffinity() it was indeed
>>> such that the master thread had the same affinity mask as the
>>> thread that it spawned. This means, that the modification of the
>>> affinity mask by a new thread in fact did affect the master thread.
>>>
>>> Executing the same codesquence however using the libnuma calls,
>>> the master thread however was not affected by the new affinity
>>> mask of the children. So clearly, libnuma must be doing something
>>> differently.
>> What distro/version of Linux are you using, and what version of
>> libnuma?
>> Libnuma v2.0.x very definitely is just a wrapper around the syscall
>> for sched_setaffinity(). I downloaded it from:
>> ftp://oss.sgi.com/www/projects/libnuma/download
>
> --
> Edgar Gabriel
> Assistant Professor
> Parallel Software Technologies Lab http://pstl.cs.uh.edu
> Department of Computer Science University of Houston
> Philip G. Hoffman Hall, Room 524 Houston, TX-77204, USA
> Tel: +1 (713) 743-3857 Fax: +1 (713) 743-3335
> _______________________________________________
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> users_at_[hidden]
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-- 
Jeff Squyres
Cisco Systems