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Subject: [OMPI users] TCP Latency
From: Andy Georgi (Andy.Georgi_at_[hidden])
Date: 2008-07-28 14:53:58

Hi all,

we use Chelsio S320E-CXA adapters
( in one of our
clusters. After tuning the kernel i measured the ping pong latency via NetPIPE and got ~12us which
is pretty good for TCP i think. So i wrote a simple ping-pong-kernel and was really terrified about
the ~45us i got with OpenMPI 1.2.6. Are there any hints how we can reduce the MPI latency? To
increase the bandwidth we already set the buffer sizes but we couldn't find a parameter which can be
relevant for the latency. Every hint is welcome.

Thanks and best regards


Dresden University of Technology
Center for Information Services
and High Performance Computing (ZIH)
D-01062 Dresden
e-mail: Andy.Georgi_at_[hidden]