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| author | Joe Thornber <ejt@redhat.com> | 2015-02-20 14:22:17 +0000 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-03-31 12:03:48 -0400 |
| commit | e65ff8703f56273c6dc8b77373f4d2bef6e35107 (patch) | |
| tree | 64f115b6ea2912e0605be69e45839d16fcf2c924 /Documentation/device-mapper | |
| parent | fdecee3224d90e51c611198baeb0c38e568ca0e8 (diff) | |
dm cache policy mq: try not to writeback data that changed in the last second
Writeback takes out a lock on the cache block, so will increase the
latency for any concurrent io.
This patch works by placing 2 sentinel objects on each level of the
multiqueues. Every WRITEBACK_PERIOD the oldest sentinel gets moved to
the newest end of the queue level.
When looking for writeback work:
if less than 25% of the cache is clean:
we select the oldest object with the lowest hit count
otherwise:
we select the oldest object that is not past a writeback sentinel.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation/device-mapper')
0 files changed, 0 insertions, 0 deletions