You are quite correct - r29719 did indeed reverse the logic of that param. Thanks for tracking it down!
I pushed a fix to the trunk and scheduled it for 1.7.4 On Jan 7, 2014, at 9:45 PM, tmish...@jcity.maeda.co.jp wrote: > > > Hi, > > I found that btl_tcp_use_nagle was negated in openmpi-1.7.4rc1, which > causes severe slowdown of tcp-network for smaller size(< 1024) in our > environment as show at the bottom. > > This happened in SVN r28719, where new MCA variable system was added. > The flag of tcp_not_use_nodelay was newly introduced as the negation of > tcp_use_nodelay in r28719(btl_tcp_component.c). > > r28361(btl_tcp_component.c): > 218 mca_btl_tcp_component.tcp_use_nodelay = > 219 !mca_btl_tcp_param_register_int ("use_nagle", "Whether to > use Nagle's algorithm or not (using Nagle's algo > rithm may increase short message latency)", 0); > > r28719(btl_tcp_component.c): > 242 mca_btl_tcp_param_register_int ("use_nagle", "Whether to use > Nagle's algorithm or not (using Nagle's algorithm > may increase short message latency)", 0, > &mca_btl_tcp_component.tcp_not_use_nodelay); > > In spite of this negation, the socket option was set by tcp_not_use_nodelay > as same as before in btl_tcp_endpoint.c. I think the line 515 should be: > > optval = !mca_btl_tcp_component.tcp_not_use_nodelay; /* tmishima */ > > I already confirmed that this fix worked well with openmpi-1.7.4rc1. > > btl_tcp_endpoint.c @ 28719 : > 514 #if defined(TCP_NODELAY) > 515 optval = mca_btl_tcp_component.tcp_not_use_nodelay; > 516 if(setsockopt(sd, IPPROTO_TCP, TCP_NODELAY, (char *)&optval, > sizeof(optval)) < 0) { > 517 BTL_ERROR(("setsockopt(TCP_NODELAY) failed: %s (%d)", > 518 strerror(opal_socket_errno), opal_socket_errno)); > 519 } > 520 #endif > > Regards, > Tetsuya Mishima > > [mishima@manage OMB-3.1.1]$ mpirun -np 2 -host manage,node05 -mca btl > self,tcp osu_bw > # OSU MPI Bandwidth Test v3.1.1 > # Size Bandwidth (MB/s) > 1 0.00 > 2 0.01 > 4 0.01 > 8 0.03 > 16 0.05 > 32 0.10 > 64 0.16 > 128 0.35 > 256 0.74 > 512 20.30 > 1024 149.89 > 2048 182.88 > 4096 203.17 > 8192 217.08 > 16384 228.58 > 32768 232.21 > 65536 169.81 > 131072 232.67 > 262144 207.03 > 524288 224.22 > 1048576 233.30 > 2097152 233.51 > 4194304 234.64 > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users