Turning on mpsafe mode by default in master

[Matthew Dillon]

:>     I'm going to remove the mplock shims in our global tokens in
:>     master, essentially running the related code mpsafe from this point
:>     on.
:
:If you get the chance, can you benchmark the difference?  I'm curious to
:see, say, the difference before and after for a buildworld/buildkernel.

    I don't think buildworld/kernel would be effected much as those are
    cpu-bound and (also) the link (ld) lines are serialized by the make
    program, so they have reached their efficiency limit.

    I do see a significant improvement when running something with a ton
    of concurrency like blogbench.  Namecache lookups can burst past
    1 million lookups/second now and regularly clock in at 600-800K
    lookups/sec.

    The one exception is when running programs which fault a lot of pages.
    A massively parallel compile, such as a bulk build, fits that bill and
    processes wind up competing for the vm_token.  This is still better than
    competing for the mp_token, though.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>