Packrats: NFSv4 client side disk caching

[Rick Macklem]

I have just put some patches up on
 	http://people.freebsd.org/~rmacklem/packrat-patches
that implement Packrat kernel threads that cache a copy of
small files on a client's local disk when an NFSv4 delegation
is issued to the client. These only work for NFSv4 mounts where
delegations are enabled and the kernel patch expects a post-FreeBSD8.1
FreeBSD-current kernel source tree. (I will try and track the
FreeBSD-current kernel with the patch. Please let me know if the
patch won't apply.)

There is no recovery from client or server crashes implemented yet and,
as such, the patches are definitely meant to be experimented with only.

They do significantly reduce the # of Read/Write RPCs for initial
experiments I've done with them and will hopefully improve performance,
particularily when working across WAN networks (larger latency).

If you choose to play with it, please let me know how it goes, rick