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Subject: Re: [OMPI users] mpool_sm_max_size disappeared ?
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-11-29 13:50:41


Gilbert Grosdidier wrote:
I found this parameter mpool_sm_max_size in this post:

But I was unable to spot it back into the 'ompi_info -all' output for v 1.4.3.
Is it still existing ?
No.
 If not, which other one is replacing it, please ?
It no longer makes any sense.

Up through OMPI 1.3.1, OMPI made crude estimates of how large the sm backing file should be.  You could limit the actual size with min and max parameters.  The problem was that the estimate was so crude that often the allocated size was excessively large while in other cases the size was insufficient to allow the job to start up.  After 1.3.1, the estimate of the size needed to start the job became much more precise.  So, the job should always at least start.  You might still want to employ a "minimum" (to give the sm area some extra room for performance reasons), but there is no longer any point in have a "maximum" size.  If you were to set a maximum that is smaller than what OMPI needs, the job wouldn't start anyhow.

You may find the FAQ useful.  Check http://www.open-mpi.org/faq/?category=sm .  There are discussions of these issues, plus ways of estimating how much room OMPI needs, therefore also ways of tuning OMPI so that it will need less.  E.g., if you think the sm area is taking up too much space, the FAQ tells you what parameters to use to make OMPI less space hungry.
Also, is it possible to specify to OpenMPI
which filesystem to use for the SM backing file, please ?
Again, check the FAQ.
http://www.open-mpi.org/faq/?category=sm#where-sm-file
Thanks in advance for any help,   Regards,   G.
De rien.