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dm cache policy smq: allow demotions to happen even during continuous IO

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dm-cache's smq policy tries hard to do it's work during the idle periods
when there is no IO.  But if there are no idle periods (eg, a long fio
run) we still need to allow some demotions and promotions to occur.

To achieve this, pass @idle=true to queue_promotion()'s
free_target_met() call so that free_target_met() doesn't short-circuit
the possibility of demotion simply because it isn't an idle period.

Fixes: b29d4986d0 ("dm cache: significant rework to leverage dm-bio-prison-v2")
Reported-by: John Harrigan <jharriga@redhat.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Joe Thornber 2017-05-03 12:01:27 -04:00 committed by Mike Snitzer
parent 7b66f13207
commit ce1d64e84d
1 changed files with 5 additions and 1 deletions
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6
drivers/md/dm-cache-policy-smq.c
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@ -1214,7 +1214,11 @@ static void queue_promotion(struct smq_policy *mq, dm_oblock_t oblock,
return;
if (allocator_empty(&mq->cache_alloc)) {
if (!free_target_met(mq, false))
/*
* We always claim to be 'idle' to ensure some demotions happen
* with continuous loads.
*/
if (!free_target_met(mq, true))
queue_demotion(mq);
return;
}