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Subject: Re: [OMPI devel] trac 1857: SM btl hangs when msg >=4k, Performance degradation ???
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-04-13 11:30:13


Jeff Squyres wrote:

> I [unfortunately] think that our benchmark performance is important.
> :-(
>
> So I don't know if 64mb is too big, but it should probably be above
> zero to avoid the performance degregation.

I don't know if 64 MB is too big. I think there is no right answer...
and you can always find situations for which your answer is the wrong
answer. I chose 64 MB because it's what everyone had lived with before
(per_peer_size=32MB with a minimum of np=2 giving 2*32MB). So, at np=2,
we mmap as much memory as before but need less of it. At large np, we
mmap enough memory (jobs will start). With any luck, we're ahead of
where we used to be.