Hi, I am trying to setup openMPI over RDMA cross machines. I call MPI_AllReduce() with a 240MB data buffer. But, it seems openMPI chunks data into small fragments (1MB ~ 15MB), and then sends them out through RDMA.
Which mca parameters can affect the message size in openMPI? How to configure "mca" to let openMPI use large message size (fragment) in data transmission? For example, is there any way we can set the mini message size of openMPI? I have followed the instructions from https://www.open-mpi.org/faq/?category=openfabrics#ofed-and-ompi. But there is no improvement in message size. I am using " --mca btl self,sm,openib ". Best, Juncheng
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