Hi again, Today I was trying with another TCP benchmark included in the hpcbench suite, and with a ping-pong test I'm also getting 100us of latency. Then, I tried with netperf and the same result....
So, in summary, I'm measuring TCP latency with messages size between 1-32 bytes: Netperf over TCP -> 100us Netpipe over TCP (NPtcp) -> 100us HPCbench over TCP -> 100us Netpipe over OpenMPI (NPmpi) -> 60us HPCBench over OpenMPI -> 60us Any clues? Thanks a lot! 2012/1/10 Roberto Rey <eros...@gmail.com> > Hi, > > I'm running some tests on EC2 cluster instances with 10 Gigabit Ethernet > hardware and I'm getting strange latency results with Netpipe and OpenMPI. > > If I run Netpipe over OpenMPI (NPmpi) I get a network latency around 60 > microseconds for small messages (less than 2kbytes). However, when I run > Netpipe over TCP (NPtcp) I always get around 100 microseconds. For bigger > messages everything seems to be OK. > > I'm using the BTL TCP in OpenMPI, so I can't understand why OpenMPI > outperforms raw TCP performance for small messages (40us of difference). I > also have run the PingPong test from the Intel Media Benchmarks and the > latency results for OpenMPI are very similar (60us) to those obtained with > NPmpi > > Can OpenMPI outperform Netpipe over TCP? Why? Is OpenMPI doing any > optimization in BTL TCP? > > The results for OpenMPI aren't so good but we must take into account the > network virtualization overhead under Xen > > Thanks for your reply > -- Roberto Rey Expósito
