ceph/ceph — pull request #1305 by liewegas (2014-02-23 20:18:18+00:00)
Title: mon: cache the min last epoch clean value

On our test 'large mon' cluster (many pgs, osds) there was *lots* of CPU
burn calculating this value. It was also observed on a DH cluster back on
bobtail.

Cache the value in memory and be somewhat intelligent about when we invalidate
our cached notion on PGMap updates.