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Subject: Re: [OMPI users] Factor of 10 loss in performance with 1.3.x
From: Mostyn Lewis (Mostyn.Lewis_at_[hidden])
Date: 2009-04-07 16:25:09


Does OpenMPI know about the number of CPUS per node for FreeBSD?

DM

On Tue, 7 Apr 2009, Ralph Castain wrote:

> I would really suggest looking at George's note first as I think you are
> chasing your tail here. It sounds like the most likely problem is that OMPI
> thinks you are oversubscribed and is setting sched_yield accordingly. which
> would fully account for these diffs.
>
> Note that the methods for setting sched yield are different between the
> various releases, so something could be catching you here. If you are sure
> you aren't oversubscribing, then set -mca mpi_yield_when_idle 0 on your cmd
> line to override any internal settings.
>
> On Apr 7, 2009, at 1:32 PM, Steve Kargl wrote:
>
>> On Tue, Apr 07, 2009 at 12:00:55PM -0700, Mostyn Lewis wrote:
>>> Steve,
>>>
>>> Did you rebuild 1.2.9? As I see you have static libraries, maybe there's
>>> a lurking phthread or something else that may have changed over time?
>>>
>>> DM
>>
>> Yes. I downloaded 1.2.9, 1.3, and 1.3.1, all within minutes of each
>> other. All are configured with --enable-static --disable-shared.
>> Each is installed in its own directory under /usr/local and
>> I use full patch names to mpicc and mpiexec.
>>
>> I just rebuilt 1.3.1 without --enable-static --disable-shared.
>> There is no change in performance. 1.3.1 is a factor of 10
>> slower than 1.2.9 with messages of ~10KB and smaller.
>>
>> I've used svn to grab trunk. Once I determine how to build
>> the trunk, I'll do a binary search to see if I can identify
>> the revision where the problem first occurs.
>>
>> --
>> Steve
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