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Subject: [OMPI users] Program hangs when using OpenMPI and CUDA
From: Fengguang Song (song_at_[hidden])
Date: 2011-06-04 18:15:39


I'm confronting a problem when using OpenMPI 1.5.1 on a GPU cluster. My program uses MPI to exchange data
between nodes, and uses cudaMemcpyAsync to exchange data between Host and GPU devices within a node.
When the MPI message size is less than 1MB, everything works fine. However, when the message size
is > 1MB, the program hangs (i.e., an MPI send never reaches its destination based on my trace).

The issue may be related to locked-memory contention between OpenMPI and CUDA.
Does anyone have the experience to solve the problem? Which MCA parameters should I tune to increase
the message size to be > 1MB (to avoid the program hang)? Any help would be appreciated.