Hi Richard, [email protected] wrote:
I would seem that a larger MTU would help in at least two situations, clearly applications with very large messages, but also those that have transmission bursts of messages below the MTU that could take advantage of hardware coalescing.
Such coalescing is typically not done in hardware. TCP with Nagle will coalesce small messages going to the same destination. However, Nagle trades latency for bandwidth, so latency junkies such as HPC apps often disable Nagle when using TCP. Some MPI implementations do coalesce small messages, mainly to look good on packet rate benchmarks.
The common MTU of 1500 was not chosen arbitrarily,
Never underestimate what a standard committee can do. Patrick _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
