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Subject: Re: [OMPI devel] poor btl sm latency
From: Matthias Jurenz (matthias.jurenz_at_[hidden])
Date: 2012-03-02 08:26:54


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
> >
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>
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