[mvapich-discuss] Processor affinity (slightly special case)

[Dhabaleswar Panda]

Without the knowledge of your application, it is very hard to know what is
going on here. However, both MVAPICH and MVAPICH2 have an option of
`blocking progress mode'. This allows you to run more number of processes
than the number of cores available. For MVAPICH2 1.4, the runtime
environmental variable to select this mode is MV2_USE_BLOCKING. More
details are available in the user guide at the following location:

http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.4rc1.html#x1-14600011.60

For MVAPICH, the rumtime environmental variable is VIADEV_USE_BLOCKING.
More details on this flag are available in the user guide at the following
location:

http://mvapich.cse.ohio-state.edu/support/mvapich_user_guide-1.1.html#x1-1040009.3.19

See if this mode helps.

Thanks,

DK

On Thu, 11 Jun 2009, Laurence Marks wrote:

> I have some jobs (large, typically > 64 cores on a dual-quadcore
> cluster) where if I run 8x8 (for instance) the master node runs into
> problems because (I think, although it's hard to be 100% certain) the
> mpi task is using too many resources, OS operations on it stop working
> or it runs out of swap and the job never completes. One solution is to
> run, for instance, 1+7+7x8 with one mpi on a single node, 7 on one and
> 8 on the rest. This is OK (inefficient) because I can run the single
> on my head node. However, then I come to a limitation because
> processor affinity on the head node means I can only run one of these
> at a time, again inefficient.
>
> I am interested in suggestions of ways around this. Some possibilities
> that I can think of:
> a) Is there a switch which would turn off processor affinity if only
> one core is being used? (I could write a shell script to do this but
> that would not be so elegant.)
> b) Is there some other way to structure the job or some alternative
> switches that might help.
>
> --
> Laurence Marks
> Department of Materials Science and Engineering
> MSE Rm 2036 Cook Hall
> 2220 N Campus Drive
> Northwestern University
> Evanston, IL 60208, USA
> Tel: (847) 491-3996 Fax: (847) 491-7820
> email: L-marks at northwestern dot edu
> Web: www.numis.northwestern.edu
> Chair, Commission on Electron Crystallography of IUCR
> www.numis.northwestern.edu/
> Electron crystallography is the branch of science that uses electron
> scattering to study the structure of matter.
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