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Subject: Re: [OMPI devel] poor btl sm latency
From: Matthias Jurenz (matthias.jurenz_at_[hidden])
Date: 2012-03-02 07:50:13


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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