[Beowulf] Re: typical latencies for gigabit ethernet

Dave Love d.love at liverpool.ac.uk
Mon Jun 29 18:43:53 EDT 2009


Rahul Nabar <rpnabar at gmail.com> writes:

> I thought so! :) Lazy person's first shot. Now I will try ethtool.

It's not relevant with all NICs.  Some use driver module parameters.

>  Any way to verify if I do?

Consult the NIC's documentation.

> Ah! So my "real" latencies are 140/2 = 70 microsecs. 

I see ping times of ~70μs between the nVidias I posted data on, and they
have an MPI latency of ~12μs.  If you want a measurement/benchmark for
MPI performance use IMB, like for the results I posted.  Otherwise
people sometimes use netpipe.  If you want basic Ethernet (Layer 2)
figures, look for Hughes-Jones' ethmon, somewhere under
http://www.hep.man.ac.uk/.

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