[Beowulf] MPI performance gain with jumbo frames

Greg Lindahl lindahl at pbm.com
Wed Jun 13 16:37:05 PDT 2007

On Wed, Jun 13, 2007 at 07:02:10PM -0400, Douglas Eadline wrote:

> So this begs the question, if we are "core rich and packet small"
> do we care about packet size and overhead?

That's not quite the question. In many programs, there is no possible
overlap between communication and computation, so they don't care how
high the overhead is, although for smaller messages lower overhead can
mean higher bandwidth (that "message rate" thing, again.)

If you can overlap, then you do care about overhead, especially for
Ethernet, where the cpu overhead is often unequally distributed over
your cores.

-- greg

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