Re: Alan Shih: "TCP IP Offloading Interface"

[Jeff Garzik <jgarzik@pobox.com>]

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.

	Jeff