block, bfq: let early-merged queues be weight-raised on split too (894df937) · Commits · 戴 / test

A just-created bfq_queue, say Q, may happen to be merged with another bfq_queue on the very first invocation of the function __bfq_insert_request. In such a case, even if Q would clearly deserve interactive weight raising (as it has just been created), the function bfq_add_request does not make it to be invoked for Q, and thus to activate weight raising for Q. As a consequence, when the state of Q is saved for a possible future restore, after a split of Q from the other bfq_queue(s), such a state happens to be (unjustly) non-weight-raised. Then the bfq_queue will not enjoy any weight raising on the split, even if should still be in an interactive weight-raising period when the split occurs. This commit solves this problem as follows, for a just-created bfq_queue that is being early-merged: it stores directly, in the saved state of the bfq_queue, the weight-raising state that would have been assigned to the bfq_queue if not early-merged. Signed-off-by:

Paolo Valente <paolo.valente@linaro.org> Tested-by:

Angelo Ruocco <angeloruocco90@gmail.com> Tested-by:

Mirko Montanari <mirkomontanari91@gmail.com> Tested-by:

Oleksandr Natalenko <oleksandr@natalenko.name> Tested-by:

Lee Tibbert <lee.tibbert@gmail.com> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/bfq-iosched.c

+23 −5

Original line number	Diff line number	Diff line
		@@ -2061,11 +2061,28 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
		bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
		bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
		bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
		if (unlikely(bfq_bfqq_just_created(bfqq) &&
		!bfq_bfqq_in_large_burst(bfqq))) {
		/*
		* bfqq being merged right after being created: bfqq
		* would have deserved interactive weight raising, but
		* did not make it to be set in a weight-raised state,
		* because of this early merge. Store directly the
		* weight-raising state that would have been assigned
		* to bfqq, so that to avoid that bfqq unjustly fails
		* to enjoy weight raising if split soon.
		*/
		bic->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff;
		bic->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd);
		bic->saved_last_wr_start_finish = jiffies;
		} else {
		bic->saved_wr_coeff = bfqq->wr_coeff;
		bic->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt;
		bic->saved_wr_start_at_switch_to_srt =
		bfqq->wr_start_at_switch_to_srt;
		bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish;
		bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
		}
		}

		static void
		bfq_merge_bfqqs(struct bfq_data bfqd, struct bfq_io_cq bic,
		@@ -4150,7 +4167,6 @@ static void __bfq_insert_request(struct bfq_data bfqd, struct request rq)
		new_bfqq->allocated++;
		bfqq->allocated--;
		new_bfqq->ref++;
		bfq_clear_bfqq_just_created(bfqq);
		/*
		* If the bic associated with the process
		* issuing this request still points to bfqq
		@@ -4162,6 +4178,8 @@ static void __bfq_insert_request(struct bfq_data bfqd, struct request rq)
		if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq)
		bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
		bfqq, new_bfqq);

		bfq_clear_bfqq_just_created(bfqq);
		/*
		* rq is about to be enqueued into new_bfqq,
		* release rq reference on bfqq

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