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Subject: [OMPI users] Over committing?
From: Rushton Martin (JMRUSHTON_at_[hidden])
Date: 2011-04-13 10:13:58

The bulk of our compute nodes are 8 cores (twin 4-core IBM x3550-m2).
Jobs are submitted by Torque/MOAB. When run with up to np=8 there is
good performance. Attempting to run with more processors brings
problems, specifically if any one node of a group of nodes has all 8
cores in use the job hangs. For instance running with 14 cores (7+7) is
fine, but running with 16 (8+8) hangs.

>From the FAQs I note the issues of over committing and aggressive
scheduling. Is it possible for mpirun (or orted on the remote nodes) to
be blocked from progressing by a fully committed node? We have a few
x3755-m2 machines with 16 cores, and we have detected a similar issue
with 16+16.

Martin Rushton
HPC System Manager, Weapons Technologies
Tel: 01959 514777, Mobile: 07939 219057
email: jmrushton_at_[hidden]
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