Mark Hahn wrote: > well, the simplest test is to connect two nodes back-to-back and run a > latency test. compare versus plugged into the switch. > (gigabit ports are all auto-mdi, so you don't need a special crossover > cable for this test.) > > I would guess that your current switch is about the same latency as the > GSM7248, but that you'll measure something like 50 us back-to-back. so > dropping 18 us will not make a dramatic difference: > ie, 70 us vs 52 - that's 25%, but it's still no where near a "real" > interconnect (myrinet, infiniband, 10G, quadrics). > > you should also verify that your nics aren't currently doing some sort > of interrupt mitigation/coalescing, since that will hurt your latency. > > if you are truely small-packet latency-bound, and unwilling to consider > a higher-performance interconnect, I think you should contemplate putting > more cores in each box. going from 2 cores per box to 8 or 16 will make a > big difference for smallish jobs that use a small number of nodes (even > if you stick to plain old gigabit).
What is GAMMA like for stability these days? It's efficiency would be compelling enough for me to do some testing, at least, were I in this situation. Going this route would also make switch latency somewhat more relevant. -- Geoffrey D. Jacobs To have no errors would be life without meaning No struggle, no joy _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
