Re: TCP vs. UDP on SMP

["Franco Travostino" <travos@nortelnetworks.com>]

>   My recollection of
> published results on using multiple
> processors for
> TCP in Unix-like operating systems is that the big gains come from
> using
> different
> processors for different connections rather than handling send and
> receive
> on a single
> connection on different processors due in part to the send/receive
> coupling
> required
> by congestion control ... but it's been a while since I've checked/read
> this
> literature.

Much agreed. Some quantitative results in:

Performance Issues in Parallelized Network Protocols, Erich M. Nahum,
David J. Yates, James
 F. Kurose, and Don Towsley. USENIX Symposium on Operating Systems
Design and
 Implementation (OSDI), Nov., 1994 (Monterey, CA).

Now that we're in TCP/IP offload age ... Recent programmable network
processors throw more silicon (e.g., hardware threads) and expose lower
level of control (e.g., asynchronous memory operations) than
general-purpose CPUs in SMP boxes. Kind of an SMP on a single chip,
really. While the TCP vs. UDP  fundamental parallelization issues
are still in the way, I expect that there will be a bunch of
parallelization trade-offs more when optimizing TCP on network
processors.

-franco