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block, bfq: set next_rq to waker_bfqq->next_rq in waker injection

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Since commit c5089591c3ba ("block, bfq: detect wakers and
unconditionally inject their I/O"), when the in-service bfq_queue, say
Q, is temporarily empty, BFQ checks whether there are I/O requests to
inject (also) from the waker bfq_queue for Q. To this goal, the value
pointed by bfqq->waker_bfqq->next_rq must be controlled. However, the
current implementation mistakenly looks at bfqq->next_rq, which
instead points to the next request of the currently served queue.

This mistake evidently causes losses of throughput in scenarios with
waker bfq_queues.

This commit corrects this mistake.

Fixes: c5089591c3ba ("block, bfq: detect wakers and unconditionally inject their I/O")
Signed-off-by: Jia Cheng Hu <jia.jiachenghu@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jia Cheng Hu 2021-01-22 19:19:44 +01:00 committed by Jens Axboe
parent b5f74ecacc
commit d4fc3640ff
1 changed files with 1 additions and 1 deletions
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2
block/bfq-iosched.c
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@ -4499,7 +4499,7 @@ static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
bfqq = bfqq->bic->bfqq[0];
else if (bfq_bfqq_has_waker(bfqq) &&
bfq_bfqq_busy(bfqq->waker_bfqq) &&
bfqq->next_rq &&
bfqq->waker_bfqq->next_rq &&
bfq_serv_to_charge(bfqq->waker_bfqq->next_rq,
bfqq->waker_bfqq) <=
bfq_bfqq_budget_left(bfqq->waker_bfqq)