Suggestion for hammer cleanup

[Matthew Dillon]

    I think a hammerd is a good idea.... or more likely a 'hammer cleanup'
    with a deamon-mode option that leaves it running in the background,
    but operating on the disk very lightly (as in very, VERY lightly) until
    the time schedule tells it that it really has to run harder.

    Implementing this would not be entirely trivial.  The only way
    it can be done properly is for the kernel HAMMER ioctls to throw in the
    load checks in the B-Tree scanning loop and to release the b-tree
    cursor locks while it is sleeping.  The sleeps can't really be done
    in the hammer user utility.

						-Matt