> >> - The network/MPI combination is fairly critical to good performance and >> to >> price/performance. I have done some benchmarks where the right MPI >> library >> on GigE produces faster results than a bad MPI library on Myrinet. Seems >> counter-intuitive, but I've seen it. >> Jeff > > Jeff, we know how some people can mess up installs, but if you have > gigabit > Ethernet, > with a one way pingpong latency of like 50-100 us if you're lucky,
Luck has very little to do with it. It is not uncommon with properly tuned GigE adapters to get 28-32 us TCP latency (measured with netpipe) However, low latency may not provide better performance in all cases. You can do better than this of course (11 us MPI latency for GigE): http://www.clustermonkey.net//content/view/121/33/1/1/ I have found the Intel NICs to work the best. Tuning the interrupt strategy is important. -- Doug > which > is > not using DMA i > guess by default; in short nonstop interrupting your cpu, > versus newer myri cards that are probably under 3 us, factor 20 to 30 > advantage to > myri then you need to really not manage to install the network to let > gigabit ethernet work better. > > That said it's not easy of course to install the network, but let's not > assume that someone who > builds a cluster doesn't manage to install the hardware he gets. > > For that huge amount of money from the highend manufacturers that you pay > for their hardware, you > DO get great support if you really don't manage to install it. > > There is not really exceptions to that. > > Vincent > >> _______________________________________________ >> Beowulf mailing list, Beowulf@beowulf.org >> To change your subscription (digest mode or unsubscribe) visit >> http://www.beowulf.org/mailman/listinfo/beowulf >> > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > -- Doug _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
