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dm cache policy smq: don't do any writebacks unless IDLE

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If there are no clean blocks to be demoted the writeback will be
triggered at that point.  Preemptively writing back can hurt high IO
load scenarios.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2017-05-11 09:09:04 -04:00 committed by Mike Snitzer
parent 49b7f76890
commit 2e63309507
1 changed files with 4 additions and 5 deletions
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9
drivers/md/dm-cache-policy-smq.c
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@ -1120,8 +1120,6 @@ static bool clean_target_met(struct smq_policy *mq, bool idle)
* Cache entries may not be populated. So we cannot rely on the
* size of the clean queue.
*/
unsigned nr_clean;
if (idle) {
/*
* We'd like to clean everything.
@ -1129,9 +1127,10 @@ static bool clean_target_met(struct smq_policy *mq, bool idle)
return q_size(&mq->dirty) == 0u;
}
nr_clean = from_cblock(mq->cache_size) - q_size(&mq->dirty);
return (nr_clean + btracker_nr_writebacks_queued(mq->bg_work)) >=
percent_to_target(mq, CLEAN_TARGET);
/*
* If we're busy we don't worry about cleaning at all.
*/
return true;
}
static bool free_target_met(struct smq_policy *mq)