K 10
svn:author
V 3
mjg
K 8
svn:date
V 27
2016-09-10T16:29:53.765971Z
K 7
svn:log
V 453
cache: improve scalability by introducing bucket locks

An array of bucket locks is added.

All modifications still require the global cache_lock to be held for
writing. However, most readers only need the relevant bucket lock and in
effect can run concurrently to the writer as long as they use a
different lock. See the added comment for more details.

This is an intermediate step towards removal of the global lock.

Reviewed by:	kib
Tested by:	pho

END