I was recently able to measure network bandwith using
NetPIPE at about 90 Mbps (100 Mbps network cards) with
both the raw TCP and MPI modules. When I do some
performance tests myself, with the code I'll be using,
the numbers come out about a factor of 10 smaller.
I'm wondering if there are any suggestions as to where
to start looking for the problem.
We are running Linux Redhat 9, using LAM 7. My code is
written in fortran 77, compiled with the Portland
Group compiler. I've been measuring the performance
with a profiling tool called Vampir. The code I run
for the test is very simple, basically consists of
starting up MPI and just doing a send_rec, then
exiting. With Vampir I can open up the trace file and
see how long it took to perform the send_rec, and also
the size of the message. For large message sizes of a
100k or so I'm only seeing 10Mbps or so. I don't
think Vampir adds much overhead to the timing, as it
didn't seem to have much effect in full scale tests of
the code.
Any suggestions?
Thanks,
Rob
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