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Subject: Re: [OMPI devel] Heads up on new feature to 1.3.4
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-08-16 17:58:25


This is an important discussion.  Do note:

1) Bind-to-core is actually the default behavior of many MPIs today.

2) The proposed OMPI bind-to-socket default is less severe.  In the general case, it would allow multiple jobs to bind in the same way without oversubscribing any core or socket.  (This comment added to the trac ticket.)

3) Defaults (if I understand correctly) can be set differently on each cluster.

Ralph Castain wrote:
There would be a "-do-not-bind" option that will prevent us from binding processes to anything which should cover that situation.

My point was only that we would be changing the out-of-the-box behavior to the opposite of today's, so all those such as yourself would now have to add the -do-not-bind MCA param to your default MCA param file.

Doable - but it -is- a significant change in our out-of-the-box behavior.

On Sun, Aug 16, 2009 at 2:14 AM, Chris Samuel <csamuel@vpac.org> wrote:

----- "Terry Dontje" <Terry.Dontje@Sun.COM> wrote:

> I just wanted to give everyone a heads up if they do not get bugs
> email.  I just submitted a CMR to move over some new paffinity options
> from the trunk to the v1.3 branch.  https://svn.open-mpi.org/trac/ompi/ticket/1997

Ralphs comments imply that for those sites that share nodes
between jobs (such as ourselves, and most other sites that
I'm aware of in Australia) these changes will severely impact
performance.

I think that would be a Very Bad Thing(tm).

Can it be something that defaults to being configured out
for at least 1.3 please ?  That way those few sites that
can take advantage can enable it whilst the rest of us
aren't impacted.