[PATCH BUGFIX/IMPROVEMENT 2/6] block, bfq: put reqs of waker and woken in dispatch list
From: Paolo Valente <hidden>
Date: 2021-01-26 12:27:55
Also in:
lkml
Subsystem:
bfq i/o scheduler, block layer, the rest · Maintainers:
Yu Kuai, Jens Axboe, Linus Torvalds
Consider a new I/O request that arrives for a bfq_queue bfqq. If, when this happens, the only active bfq_queues are bfqq and either its waker bfq_queue or one of its woken bfq_queues, then there is no point in queueing this new I/O request in bfqq for service. In fact, the in-service queue and bfqq agree on serving this new I/O request as soon as possible. So this commit puts this new I/O request directly into the dispatch list. Tested-by: Jan Kara <jack@suse.cz> Signed-off-by: Paolo Valente <redacted> --- block/bfq-iosched.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index a83149407336..e5b83910fbe0 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c@@ -5640,7 +5640,22 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, spin_lock_irq(&bfqd->lock); bfqq = bfq_init_rq(rq); - if (!bfqq || at_head || blk_rq_is_passthrough(rq)) { + + /* + * Additional case for putting rq directly into the dispatch + * queue: the only active bfq_queues are bfqq and either its + * waker bfq_queue or one of its woken bfq_queues. In this + * case, there is no point in queueing rq in bfqq for + * service. In fact, the in-service queue and bfqq agree on + * serving this new I/O request as soon as possible. + */ + if (!bfqq || + (bfqq != bfqd->in_service_queue && + bfqd->in_service_queue != NULL && + bfq_tot_busy_queues(bfqd) == 1 + bfq_bfqq_busy(bfqq) && + (bfqq->waker_bfqq == bfqd->in_service_queue || + bfqd->in_service_queue->waker_bfqq == bfqq)) || + at_head || blk_rq_is_passthrough(rq)) { if (at_head) list_add(&rq->queuelist, &bfqd->dispatch); else
--
2.20.1