FYI: merging TCP, UDP, netisr locking changes

[Robert Watson]

Dear all:

Over the next few days, I will be merging a number of TCP-related locking 
changes, as well as changes to various network stack infrastructure bits, such 
as the netisr implementation.  The goal, generally, has been to move us in the 
direction of supporting more clear CPU affinity for network flows, the ability 
to program filters in network cards to support those affinities explicitly, 
and elimination of cache line contention (whether by locks, stats, etc) during 
high-volume parallel steady-state TCP load, with ancillary benefits 
(hopefully) for UDP and other protocols.  This has implied non-trivial changes 
to our inpcb locking model, netisr code, etc.  Detailed information will 
appear in commit messages as I go; some elements, such a programming of card 
filters based on setting TCP socket options, are very much a work in progress.

Obviously, there are no bugs in this code at all.  However, if they are, they 
might manifest as network problems, new WITNESS warnings, etc, and network 
stack exercise + reports would be greatly appreciated!

This work has been sponsored by Juniper Networks.  Thanks also to Bjoern Zeeb, 
who has been reviewing changes!

Robert N M Watson
Computer Laboratory
University of Cambridge