Open MPI logo

Open MPI Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Development mailing list

Subject: Re: [OMPI devel] poor btl sm latency
From: Jeffrey Squyres (jsquyres_at_[hidden])
Date: 2012-03-02 08:58:45


Ok. Good that there's no oversubscription bug, at least. :-)

Did you see my off-list mail to you yesterday about building with an external copy of hwloc 1.4 to see if that helps?

On Mar 2, 2012, at 8:26 AM, Matthias Jurenz wrote:

> To exclude a possible bug within the LSF component, I rebuilt Open MPI without
> support for LSF (--without-lsf).
>
> -> It makes no difference - the latency is still bad: ~1.1us.
>
> Matthias
>
> On Friday 02 March 2012 13:50:13 Matthias Jurenz wrote:
>> SORRY, it was obviously a big mistake by me. :-(
>>
>> Open MPI 1.5.5 was built with LSF support, so when starting an LSF job it's
>> necessary to request at least the number of tasks/cores as used for the
>> subsequent mpirun command. That was not the case - I forgot the bsub's '-n'
>> option to specify the number of task, so only *one* task/core was
>> requested.
>>
>> Open MPI 1.4.5 was built *without* LSF support, so the supposed misbehavior
>> could not happen with it.
>>
>> In short, there is no bug in Open MPI 1.5.x regarding to the detection of
>> oversubscription. Sorry for any confusion!
>>
>> Matthias
>>
>> On Tuesday 28 February 2012 13:36:56 Matthias Jurenz wrote:
>>> When using Open MPI v1.4.5 I get ~1.1us. That's the same result as I get
>>> with Open MPI v1.5.x using mpi_yield_when_idle=0.
>>> So I think there is a bug in Open MPI (v1.5.4 and v1.5.5rc2) regarding to
>>> the automatic performance mode selection.
>>>
>>> When enabling the degraded performance mode for Open MPI 1.4.5
>>> (mpi_yield_when_idle=1) I get ~1.8us latencies.
>>>
>>> Matthias
>>>
>>> On Tuesday 28 February 2012 06:20:28 Christopher Samuel wrote:
>>>> On 13/02/12 22:11, Matthias Jurenz wrote:
>>>>> Do you have any idea? Please help!
>>>>
>>>> Do you see the same bad latency in the old branch (1.4.5) ?
>>>>
>>>> cheers,
>>>> Chris
>>>
>>> _______________________________________________
>>> devel mailing list
>>> devel_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel

-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/