[Beowulf] Q: IB message rate & large core counts (per node)?

Greg Lindahl lindahl at pbm.com
Tue Feb 23 16:29:04 EST 2010


On Fri, Feb 19, 2010 at 02:36:34PM -0800, Gilad Shainer wrote:

> Nice to hear from you Greg, hope all is well.

I hope all is well with you, Gilad. From what I can tell, you're again
visiting that alternate Universe that you sometimes visit -- is it
nice there?

> I don't forget anything, at least for now. OSU has different benchmarks
> so you can measure message coalescing or real message rate. Funny to
> read that Q hated coalescing when they created the first benchmark for
> that

The benchmark that we created is not a coalescing benchmark.

Coalescing produces a meaningless answer from the message rate
benchmark. Real apps don't get much of a benefit from message
coalescing, but (if they send smallish messages) they get a big
benefit from a good non-coalesced message rate.

If you look back in the archives of this list, you can find me saying
that. And some other people were involved in the discussion, too.

Or, we can take your word for what happened, instead of looking at
history. I know which method you prefer.

-- greg


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