Sorry, the kernel is 2.6.32.12, not 2.6.32.2. And I forgot to mention the system is CentOS 5.4.
And further ... 25MB/s is after tweaking btl_sm_num_fifos=8 and btl_sm_eager_limit=65536. Without those the rate is 9MB/s for 1MB packets and 1.5MB/s for 10kB packets :-( On 05/11/2010 08:19 PM, Oskar Enoksson wrote: > I have a cluster with two Intel Xeon Nehalem E5520 CPU per server > (quad-core, 2.27GHz). The interconnect is 4xQDR Infiniband (Mellanox > ConnectX). > > I have compiled and installed OpenMPI 1.4.2. The kernel is 2.6.32.2 and > I have compiled the kernel myself. I use gridengine 6.2u5. Openmpi was > compiled with "--with-libnuma --with-sge. > > The problem is that I get very bad performance unless I explicitly > exclude the "sm" btl and I can't figure out why. I have tried searching > the web and the OpenMPI mailing lists. I have seen reports about > non-optimal performance, but my results are far worse than any other > reports I have found. > > I run the "mpi_stress" program with different packet lengths. I run on a > single server using 8 slots so that all eight cores on one server are > occupied. > > When I use "-mca btl self,openib" I get pretty good results, between > 450MB/s and 700MB/s depending on the packet lengths. When I use "-mca > btl self,sm" or "-mca btl self,sm,openib" I just get 25MB/s to 30MB/s > for packet length 1MB. For 10kB packets the results are around 5MB/s. > things get abour 20% faster if I set "-mca paffinity_alone 1". > > What is going on? Any hints? I thought these CPU's had excellent > SM-bandwidth over quickpath. I expected several GB/s. > > Hyperthreading is enabled, if that is relevant. The locked-memory limit > is 500MB and the stack limit is 64MB. > > Please help! > Thanks > /Oskar > >
