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Subject: Re: [OMPI devel] kernel 2.6.23 vs 2.6.24 - communication/wait times
From: Oliver Geisler (openmpi_at_[hidden])
Date: 2010-04-19 11:12:55


> Ah, that could do it. Open MPI's shared memory files are under /tmp. So if /tmp is NFS, you could get extremely high latencies because of dirty page writes out through NFS.
>
> You don't necessarily have to make /tmp disk-full -- if you just make OMPI's session directories go into a ramdisk instead of to NFS, that should also be sufficient.
>

I just browsed FAQ and "ompi_info --param all all", but didn't find the
answer:
How do I set the OMPI session directory to point it to a ramdisk?

And another question:
What would be a good size for the ram disk? One general value was
supposed by the FAQ with 128MB, but what is your experience?
(maybe a large topic by itself, so I have to try out, I guess)

Thanks a lot.

Oli

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