From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Jia Cheng Hu <jia.jiachenghu@gmail.com>, Jan Kara <jack@suse.cz>,
Paolo Valente <paolo.valente@linaro.org>
Subject: [PATCH BUGFIX/IMPROVEMENT 2/6] block, bfq: set next_rq to waker_bfqq->next_rq in waker injection
Date: Fri, 22 Jan 2021 19:19:44 +0100 [thread overview]
Message-ID: <20210122181948.35660-3-paolo.valente@linaro.org> (raw)
In-Reply-To: <20210122181948.35660-1-paolo.valente@linaro.org>
From: Jia Cheng Hu <jia.jiachenghu@gmail.com>
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>
---
block/bfq-iosched.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index eb2ca32d5b63..fdc5e163b2fe 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -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)
--
2.20.1
next prev parent reply other threads:[~2021-01-22 19:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 18:19 [PATCH BUGFIX/IMPROVEMENT 0/6] block, bfq: first bath of fixes and improvements Paolo Valente
2021-01-22 18:19 ` [PATCH BUGFIX/IMPROVEMENT 1/6] block, bfq: use half slice_idle as a threshold to check short ttime Paolo Valente
2021-01-22 18:19 ` Paolo Valente [this message]
2021-01-22 18:19 ` [PATCH BUGFIX/IMPROVEMENT 3/6] block, bfq: increase time window for waker detection Paolo Valente
2021-01-22 18:19 ` [PATCH BUGFIX/IMPROVEMENT 4/6] block, bfq: do not raise non-default weights Paolo Valente
2021-01-22 18:19 ` [PATCH BUGFIX/IMPROVEMENT 5/6] block, bfq: avoid spurious switches to soft_rt of interactive queues Paolo Valente
2021-01-22 18:19 ` [PATCH BUGFIX/IMPROVEMENT 6/6] block, bfq: do not expire a queue when it is the only busy one Paolo Valente
2021-01-22 18:22 ` [PATCH BUGFIX/IMPROVEMENT 0/6] block, bfq: first bath of fixes and improvements Paolo Valente
2021-01-25 1:18 ` Jens Axboe
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