HEADS UP - major structure size changes in HEAD

[Matthew Dillon]

    The recent lwkt_token revamp significantly changes the size of
    miscellanious structures in the HEAD branch.  A full kernel + modules
    recompile is recommended for people tracking HEAD.

    These lwkt_token changes will make it a lot easier for us to proceed
    on the MPSAFE work.  The simplified API makes tokens much easier
    to work with now.

    The acquisition and release of recursive tokens is also now virtually
    free (not even atomic ops are needed), meaning that developers doing
    MPSAFE work can acquire a token multiple times in a deep call paths
    without having to worry about any loss of performance.  This will
    make locking up the APIs a lot easier.

    We want to use tokens for locking up major system APIs with deep
    call paths (e.g. I/O, VM, PMAP, etc) because tokens are not subject
    to lock order reversals, so they can be acquired in any order.  This
    is needed since these major system APIs call each other back and
    forth.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>