Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] mpirun only works when -np <4 (Gus Correa)
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2009-12-15 14:55:52


Matthew MacManes wrote:

>On my system, mpirun -np 8 -mca btl_sm_num_fifos 7 is much slower (and appeared to hang after several thousand interations) than -mca btl ^sm
>
>
If the hang is reproducible, we should perhaps have a look. Also, the
fact that it's much slower is interesting. Can you characterize the
message pattern? Increasing the number of FIFOs means that there are
more places to look to find messages, but this should make a difference
mainly only for very large on-node process counts (more than 8 I would
have thought) and very latency-sensitive applications (but perhaps
that's what you have).

>Is there another better way I should be modifying fifos to get better performance?
>
>
Actually, there have some been some promising developments on the
trac-2043 front. So, maybe 1-3 days of patience could payoff here.
But, I'm not in a position to promise anything.

>On Dec 11, 2009, at 4:04 AM, Terry Dontje wrote:
>
>
>>>Date: Thu, 10 Dec 2009 17:57:27 -0500
>>>From: Jeff Squyres <jsquyres_at_[hidden]>
>>>
>>>On Dec 10, 2009, at 5:53 PM, Gus Correa wrote:
>>>
>>>
>>>>>How does the efficiency of loopback
>>>>>(let's say, over TCP and over IB) compare with "sm"?
>>>>>
>>>>>
>>>Definitely not as good; that's why we have sm. :-) I don't have any quantification of that assertion, though (i.e., no numbers to back that up).
>>>
>>>
>>However, as Eugene wrote earlier you can actually increase the number of fifos used by the SM and avoid the hang that way. Unless you are really strapped for memory I think that would be the best way to go.
>>
>>