hash with names of its hooks. It starts with size of 16, and
grows when number of hooks reaches twice the current size. A
failure to grow (memory is allocated with M_NOWAIT) isn't
fatal, however.
I used standard hash(9) function for the hash. With 25000
hooks named in the mpd (ports/net/mpd5) manner of "b%u", the
distributions is the following: 72.1% entries consist of one
element, 22.1% consist of two, 5.2% consist of three and
0.6% of four.
Speedup in a synthetic test that creates 25000 hooks and then
runs through a long cyclce dereferencing them in a random order
is over 25 times.