[Beowulf] 1.2 us IB latency?
hahn at mcmaster.ca
Wed Apr 18 08:14:34 EDT 2007
>> in anycase, if this is a non-streaming latency result, it's
>> pretty good; enough to make quadrics look comprehensively out
>> of the picture (guess they've switched horses to 10GE anyway.)
> It is a non-streaming latency on Mellanox ConnectX. On MPI it
> is 1.2us latency - Pallas MPI Ping.
this is something like 3x better than previous IB - a difference
of that magnitude must always raise eyebrows. how was such a
dramatic improvement made? what was so badly broken in previous
incarnations? is there some caveat to the new score, like requiring
all of userspace to be pre-pinned, or buffers to be 4k aligned or something?
also, just to be perfectly explicit, this is 1.2 us inter-node,
right? not something crazy like two 8-core boxes with only two
of 16 hops inter-box?
thanks, mark hahn.
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