tree 47ffaceb2c4c977ab639810d6812a356f364def4
parent b815805154cc62debbc423a6c27ae39290b300ae
author Joe Thornber <ejt@redhat.com> 1386593585 +0000
committer Mike Snitzer <snitzer@redhat.com> 1389107673 -0500

dm cache policy mq: introduce three promotion threshold tunables

Internally the mq policy maintains a promotion threshold variable.  If
the hit count of a block not in the cache goes above this threshold it
gets promoted to the cache.

This patch introduces three new tunables that allow you to tweak the
promotion threshold by adding a small value.  These adjustments depend
on the io type:

   read_promote_adjustment:    READ io, default 4
   write_promote_adjustment:   WRITE io, default 8
   discard_promote_adjustment: READ/WRITE io to a discarded block, default 1

If you're trying to quickly warm a new cache device you may wish to
reduce these to encourage promotion.  Remember to switch them back to
their defaults after the cache fills though.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>