Hi, i'm testing SKaMPI Benchmark on IBM Blade System over Infiniband. Current version of OpenMPI is 1.2.6 I have tried to disable RDMA setting btl_openib_use_eager_rdma = 0. But, i have noted that, in MPI collectives execution time, there are few difference beetween RDMA active and none. Before tests, I expected that with RDMA off, excecution time was more long.
So, i suppose that SKaMPI benchmark does continues reallocation of buffers that forbid benefits of RDMA protocol. Indeed, if initial buffer address change every time, we have to do very much registration of memory pages afterwards decay of perfomance. I used RDMA pipeline protocol. This protocol should makes no assumption about the application reuse of source and target buffers. But, is it every true? Parameters net are explained below. MCA btl: parameter "btl_openib_mpool" (current value: "rdma") MCA btl: parameter "btl_openib_ib_max_rdma_dst_ops" (current value: "4") MCA btl: parameter "btl_openib_use_eager_rdma" (current value: "1") MCA btl: parameter "btl_openib_eager_rdma_threshold" (current value: "16") MCA btl: parameter "btl_openib_max_eager_rdma" (current value: "16") MCA btl: parameter "btl_openib_eager_rdma_num" (current value: "16") MCA btl: parameter "btl_openib_min_rdma_size" (current value: "1048576") MCA btl: parameter "btl_openib_max_rdma_size" (current value: "1048576") -- Gabriele Fatigati CINECA Systems & Tecnologies Department Supercomputing Group Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy www.cineca.it Tel: +39 051 6171722 g.fatig...@cineca.it
