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Subject: Re: [OMPI devel] OpenMPI, PLPA and Linux cpuset/cgroup support
From: Sylvain Jeaugey (sylvain.jeaugey_at_[hidden])
Date: 2009-07-22 11:17:28


Hi Jeff,

I'm interested in joining the effort, since we will likely have the same
problem with SLURM's cpuset support.

On Wed, 22 Jul 2009, Jeff Squyres wrote:

> But as to why it's getting EINVAL, that could be wonky. We might want to
> take this to the PLPA list and have you run some small, non-MPI examples to
> ensure that PLPA is parsing your /sys tree properly, etc.
I don't see the /sys implication here. Can you be more precise on which
files are read to determine placement ?

IIRC, when you are inside a cpuset, you can see all cpus (/sys should be
unmodified) but calling set_schedaffinity with a mask containing a cpu
outside the cpuset will return EINVAL. The only solution I see to solve
this would be to get the "allowed" cpus with sched_getaffinity,
which should be set according to the cpuset mask.

Sylvain