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Subject: Re: [OMPI users] anybody tried OMPI with gpudirect?
From: Rolf vandeVaart (rvandevaart_at_[hidden])
Date: 2011-02-28 11:30:34

Hi Brice:
Yes, I have tired OMPI 1.5 with gpudirect and it worked for me. You definitely need the patch or you will see the behavior just as you described, a hang. One thing you could try is disabling the large message RDMA in OMPI and see if that works. That can be done by adjusting the openib BTL flags.

-- mca btl_openib_flags 304


-----Original Message-----
From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On Behalf Of Brice Goglin
Sent: Monday, February 28, 2011 11:16 AM
To: users_at_[hidden]
Subject: [OMPI users] anybody tried OMPI with gpudirect?


I am trying to play with nvidia's gpudirect. The test program given with the gpudirect tarball just does a basic MPI ping-pong between two process that allocated their buffers with cudaHostMalloc instead of malloc. It seems to work with Intel MPI but Open MPI 1.5 hangs in the first MPI_Send. Replacing the cuda buffer with a normally-malloc'ed buffer makes the program work again. I assume that something goes wrong when OMPI tries to register/pin the cuda buffer in the IB stack (that's what gpudirect seems to be about), but I don't see why Intel MPI would succeed there.

Has anybody ever looked at this?

FWIW, we're using OMPI 1.5, OFED 1.5.2, Intel MPI and SLES11 w/ and w/o the gpudirect patch.

Brice Goglin

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