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Subject: Re: [OMPI devel] kernel 2.6.23 vs 2.6.24 - communication/wait times
From: Rainer Keller (keller_at_[hidden])
Date: 2010-04-06 11:11:51


Hello Oliver,
Hmm, this is really a teaser...
I haven't seen such a drastic behavior, and haven't read of any on the list.

One thing however, that might interfere is process binding.
Could You make sure, that processes are not bound to cores (default in 1.4.1):
with mpirun --bind-to-none

Just an idea...

Regards,
Rainer

On Tuesday 06 April 2010 10:07:35 am Oliver Geisler wrote:
> Hello Devel-List,
>
> I am a little bit helpless about this matter. I already posted in the
> user list. In case you don't read the users list, I post in here.
>
> This is the original posting:
>
> http://www.open-mpi.org/community/lists/users/2010/03/12474.php
>
> Short:
> Switching from kernel 2.6.23 to 2.6.24 (and up), using openmpi 1.2.7-rc2
> (I know outdated, but in debian stable, and same results with 1.4.1)
> increases communication times between processes (essentially between one
> master and several slave processes). This is regardless of whether the
> processes are local only or communication is over ethernet.
>
> Did anybody witness such a behavior?
>
> Ideas what should I test for?
>
> What additional information should I provide for you?
>
> Thanks for your time
>
> oli
>

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Rainer Keller, PhD                  Tel: +1 (865) 241-6293
Oak Ridge National Lab          Fax: +1 (865) 241-4811
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