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* dm cache policy mq: introduce three promotion threshold tunablesJoe Thornber2014-01-071-2/+14
| | | | | | | | | | | | | | | | | | | | | 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>
* dm cache policy mq: implement writeback_work() and mq_{set,clear}_dirty()Joe Thornber2013-11-101-2/+4
| | | | | | | | | | | | | | | | There are now two multiqueues for in cache blocks. A clean one and a dirty one. writeback_work comes from the dirty one. Demotions come from the clean one. There are two benefits: - Performance improvement, since demoting a clean block is a noop. - The cache cleans itself when io load is light. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm cache: add cleaner policyHeinz Mauelshagen2013-03-011-0/+5
| | | | | | | | | | A simple cache policy that writes back all data to the origin. This is used to decommission a dm cache by emptying it. Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm cache: add mq policyJoe Thornber2013-03-011-0/+72
A cache policy that uses a multiqueue ordered by recent hit count to select which blocks should be promoted and demoted. This is meant to be a general purpose policy. It prioritises reads over writes. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>