Review of patch that makes NFSv4 server hash table sizing tunable

[Rick Macklem]

I think the subject line says it. There is a patch..
  https://reviews.freebsd.org/D2596
which makes the hash table sizes for the NFSv4 server tunable.

It does not change the default sizes of the hash tables and,
since these tables are only used by NFSv4, should have no effect
on NFSv3. I do not believe there is sufficient experience with
the NFSv4 server under heavy client load to autotune these hash
tables, but hopefully tunable hash table sizing will provide
further experience/testing of different sizes.

Testing of a single client did not show that larger tables had
any significant effect on performance, but a server handling many
NFSv4 clients may need larger tables.

Please review/comment on this patch, rick