[Beowulf] VMC - Virtual Machine Console

Chris Samuel csamuel at vpac.org
Sat Feb 23 22:55:58 EST 2008


----- "stephen mulcahy" <smulcahy at aplpi.com> wrote:

> As a further aside, some MPI libraries (OpenMPI comes to mind) seem to
> make some efforts to keep processes on the same cores also (or can be
> instructed to via a run-time option).

At one point MVAPICH2 would enable this by default
on AMD Opteron - but always started from core 0 when
binding processes.

So if you had an 8 core box and 2 x 4 CPU jobs were
run on it they'd both end up fighting over cores 0-3
whilst cores 4-7 sat in a corner twiddling their
thumbs and wondering why they had no work to do. :-(

It got even worse if you launched 4 x 2 CPU jobs..

-- 
Christopher Samuel - (03) 9925 4751 - Systems Manager
 The Victorian Partnership for Advanced Computing
 P.O. Box 201, Carlton South, VIC 3053, Australia
VPAC is a not-for-profit Registered Research Agency
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