[torqueusers] IB epilogoue/prolog, and any other concerns

Walid walid.shaari at gmail.com
Fri May 30 01:49:09 MDT 2008


Hi Chris,

2008/5/30 Chris Samuel <csamuel at vpac.org>:

>
> We started off with MVAPICH but moved to OpenMPI when we
> found we had real problems getting any job larger than 64
> CPUs to start with it.


I am taking much larger number than  that in terms of cores, and wondering
what would be the overhead on connections, and as a result on system
resources associated with this connection, and that most likely means some
parameters that i need to tune, and have in place.

>
>
> OpenMPI also has *much* better error messages, and doesn't
> have the dumb idea of enabling CPU affinity by default on
> AMD64 systems (though that might be fixed by now).


you mean OpenMPI does handle CPU affinity by default or that is something I
should be worried about? in AMD64 most likely i should worry, however we are
using Intel Harpertown E5450, unless the developer submits a 2 core job in
an 8 core node, should i worry how to make sure that each core is a
differenty cpu at least?

>
> Their code naively binds from cores 0->N, which is fine
> until you run two 4 CPU codes on an 8 core node and why
> they're running at half speed compared to just running
> one job on its own.. :-(


Interesting!


regards

Walid.
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