Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] Factor of 10 loss in performance with 1.3.x
From: Steve Kargl (sgk_at_[hidden])
Date: 2009-04-10 17:30:20


On Fri, Apr 10, 2009 at 05:10:29PM -0400, Jeff Squyres wrote:
> On Apr 7, 2009, at 4:25 PM, Mostyn Lewis wrote:
>
> >Does OpenMPI know about the number of CPUS per node for FreeBSD?
> >
>
> This is exactly the right question: apparently it does not.
>
> Specifically, it looks like we have a bad configure test in the
> "posix" paffinity component which triggers it to not be built. Hence,
> OMPI *always* thinks there's only 1 processor.
>
> The setup for how to get the number of processors was totally changed
> between the 1.2 and 1.3 series. I think that this completely explains
> the issue (OMPI didn't have a paffinity component, so it assumed 1
> processor, then it saw that there were 2 processes running, and
> therefore decided that it was running in oversubscribed mode).
>
> I'll fix. I don't know if it'll make the cut for 1.3.2 or not.
>

Thanks for looking into this issue. As a side note, FreeBSD 7.1
and higher has the cpuset_getaffinity/cpuset_setaffinity system
calls. I suspect that at some point openmpi can have a
opal/mca/paffinity/freebsd directory with an appropriate set of
paffinity_* files.

-- 
Steve