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Subject: Re: [OMPI users] RDMA-CM
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-06-17 07:19:59

On Jun 17, 2008, at 5:12 AM, Neeraj Chourasia wrote:

> I downloaded openmpi-1.3 version from night tarballs to check
> RDMA-CM support. I am able to compile and install it, but dont know
> how to run it as there is no documentation provided. Did someone try
> running it with OpenMPI?

The theme of Open MPI is that we try to do most things under the
covers. As such, if RDMA CM support is detected, we'll try to use it
at run time. You can force it with the following MCA parameter,

     mpirun --mca btl_openib_cpc_include rdmacm ...

"CPC" is our acronym of how the openib BTL establishes connections.
The btl_openib_cpc_include MCA param allows you to specify a comma-
delimited list of CPCs to use.

Note that there is still one feature missing for the RDMA CM (and IB
CM) support -- a progress thread for connections. We've found that
for applications that do not dip into the MPI layer frequently, RDMA /
IB CM connections can timeout. We're in the middle of adding a
progress thread for openib BTL connections.

> My another question is Does OpenMPI1.3 has progress-threads support
> for IB? Because while compiling with that option, it didnt give me
> any warnings or failure unlike openmpi1.2.X series does.

No, progress threads are not yet supported for the openib BTL.

Jeff Squyres
Cisco Systems