Re: Alan Shih: "TCP IP Offloading Interface"

Jeff Garzik (
Mon, 14 Jul 2003 16:03:01 -0400

David griego wrote:
> Intel Clusters and Network Storage Volume Platforms Lab reported that it
> takes about 1MHz to process 1Mbps on a PIII. Using this rule of thumb
> (they showed it scaling from 400MHz to 800MHz) it would take 10GHz to
> process 10Mbps. Well you might say "what about multi-processers?" This

Um. It doesn't take nearly 10Ghz to handle 10Mbps, or even 100Mbps.

> would be good for people that have multi-processors, but there is a
> large segment of embedded processors that are not going have SMP, or be
> at 10GHz anytime soon. Besides that processing interrupts does not
> scale across MPs liniarly. The truth is that communication speeds are
> outpacing processor speeds at this time.

If the host CPU is a bottleneck after large-send and checksums have been
offloaded, then logically you aren't getting any work done _anyway_.
You have to interface with the net stack at some point, in which case
you incur a fixed cost, for socket handling, TCP exception handling, etc.

Maybe somebody needs to be looking into AMP (asymmetric
multiprocessing), too.


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