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block, bfq: port commit "cfq-iosched: improve hw_tag detection"

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The original commit is commit 1a1238a7dd ("cfq-iosched: improve hw_tag
detection") and has the following commit message:

If active queue hasn't enough requests and idle window opens, cfq will
not dispatch sufficient requests to hardware. In such situation, current
code will zero hw_tag. But this is because cfq doesn't dispatch enough
requests instead of hardware queue doesn't work. Don't zero hw_tag in
such case.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Paolo Valente 2019-01-29 12:06:36 +01:00 committed by Jens Axboe
parent a3c9256032
commit b3c3498112
1 changed files with 13 additions and 0 deletions
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13
block/bfq-iosched.c
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@ -4786,6 +4786,8 @@ static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
static void bfq_update_hw_tag(struct bfq_data *bfqd)
{
struct bfq_queue *bfqq = bfqd->in_service_queue;
bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver,
bfqd->rq_in_driver);
@ -4801,6 +4803,17 @@ static void bfq_update_hw_tag(struct bfq_data *bfqd)
if (bfqd->rq_in_driver + bfqd->queued <= BFQ_HW_QUEUE_THRESHOLD)
return;
/*
* If active queue hasn't enough requests and can idle, bfq might not
* dispatch sufficient requests to hardware. Don't zero hw_tag in this
* case
*/
if (bfqq && bfq_bfqq_has_short_ttime(bfqq) &&
bfqq->dispatched + bfqq->queued[0] + bfqq->queued[1] <
BFQ_HW_QUEUE_THRESHOLD &&
bfqd->rq_in_driver < BFQ_HW_QUEUE_THRESHOLD)
return;
if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
return;