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Subject: Re: [OMPI users] Mixing Linux's CPU-shielding with mpirun's bind-to-core
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2013-08-18 11:50:47

Le 18/08/2013 14:51, Siddhartha Jana a écrit :
> If all the above works and does not return errors (you should
> check that
> your application's PID is in /dev/cpuset/socket0/tasks while running),
> bind-to-core won't clash with it, at least when using a OMPI that uses
> hwloc for binding (v1.5.2 or later if I remember correctly).
> My concern is that hwloc is used before the application begins
> executing and so mpirun might use it to bind the application to
> different cores than the ones I want them to bind to.

Ah right, they could be a problem here. MPI can bind at two different
times: inside mpirun after ssh before running the actual program (this
one would ignore your cpuset), later at MPI_Init inside your program
(this one will ignore your cpuset only if you call MPI_Init before
creating the cpuset).

I'll let OMPI people give more details about this.