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block, bfq: let also stably merged queues enjoy weight raising 

Merged bfq_queues are kept out of weight-raising (low-latency)
mechanisms. The reason is that these queues are usually created for
non-interactive and non-soft-real-time tasks. Yet this is not the case
for stably-merged queues. These queues are merged just because they
are created shortly after each other. So they may easily serve the I/O
of an interactive or soft-real time application, if the application
happens to spawn multiple processes.

To address this issue, this commits lets also stably-merged queued
enjoy weight raising.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Link: https://lore.kernel.org/r/20210619140948.98712-2-paolo.valente@linaro.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Paolo Valente 2021-06-19 16:09:42 +02:00 committed by Jens Axboe
parent 76a8040817
commit 511a269923
1 changed files with 14 additions and 1 deletions
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15
block/bfq-iosched.c
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@ -1729,10 +1729,23 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
bfqq->entity.new_weight == 40;
*interactive = !in_burst && idle_for_long_time &&
bfqq->entity.new_weight == 40;
/*
* Merged bfq_queues are kept out of weight-raising
* (low-latency) mechanisms. The reason is that these queues
* are usually created for non-interactive and
* non-soft-real-time tasks. Yet this is not the case for
* stably-merged queues. These queues are merged just because
* they are created shortly after each other. So they may
* easily serve the I/O of an interactive or soft-real time
* application, if the application happens to spawn multiple
* processes. So let also stably-merged queued enjoy weight
* raising.
*/
wr_or_deserves_wr = bfqd->low_latency &&
(bfqq->wr_coeff > 1 ||
(bfq_bfqq_sync(bfqq) &&
bfqq->bic && (*interactive || soft_rt)));
(bfqq->bic || RQ_BIC(rq)->stably_merged) &&
(*interactive || soft_rt)));
/*
* Using the last flag, update budget and check whether bfqq