Hi I have a small test network that I'm using to do some number crunching for my dissertation. My network consists of three machines with intel gigabit network cards (all em drivers with two hosts setup as laggs) with default MTU settings etc... running Freebsd 9.1 and mpich2.
when I run mpdringtest I get latencies of:
time for 1 loops = 0.00105500221252 seconds time for 2 loops = 0.101227998734 seconds time for 3 loops = 0.200784921646 seconds time for 4 loops = 0.300806045532 seconds time for 10 loops = 0.942656040192 seconds time for 100 loops = 11.5054900646 seconds
the network latency is:
Max Latency: from \ to city17 glados blackmesa city17 0.335 0.739 glados 0.319 0.689 blackmesa 0.992 0.746 Mean Latency: from \ to city17 glados blackmesa city17 0.205 0.525 glados 0.195 0.518 blackmesa 0.599 0.503 for hosts city17:8 glados:4 blackmesa:4
Based on my assumptions each loop should take approximately about the sum of the upper or lower triangular portion of the mean latency matrix (attained via ping). This seems to match the one ring results. However for more than one ring the latency seems to increase considerably. I read the manpage on this topic and it didn't really explain much besides saying it passed a message around in a ring. Are these results fairly normal w.r.t. latency and mdpringresults?
The switch is an HP procurve 1810g-8 if it matters (no other traffic is running through the switch).