Commit 2110858c authored by Yu Kuai's avatar Yu Kuai Committed by Jens Axboe
Browse files

block, bfq: convert to use request_queue->async_depth 



The default limits is unchanged, and user can configure async_depth now.

Signed-off-by: default avatarYu Kuai <yukuai@fnnas.com>
Reviewed-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 988bb1b9

block/bfq-iosched.c

+17 −26
Original line number Diff line number Diff line
@@ -7112,39 +7112,29 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg) 
static void bfq_depth_updated(struct request_queue *q)

{

	struct bfq_data *bfqd = q->elevator->elevator_data;

	unsigned int nr_requests = q->nr_requests;

	unsigned int async_depth = q->async_depth;



	/*

	 * In-word depths if no bfq_queue is being weight-raised:

	 * leaving 25% of tags only for sync reads.

	 * By default:

	 *  - sync reads are not limited

	 * If bfqq is not being weight-raised:

	 *  - sync writes are limited to 75%(async depth default value)

	 *  - async IO are limited to 50%

	 * If bfqq is being weight-raised:

	 *  - sync writes are limited to ~37%

	 *  - async IO are limited to ~18

	 *

	 * In next formulas, right-shift the value

	 * (1U<<bt->sb.shift), instead of computing directly

	 * (1U<<(bt->sb.shift - something)), to be robust against

	 * any possible value of bt->sb.shift, without having to

	 * limit 'something'.

	 * If request_queue->async_depth is updated by user, all limit are

	 * updated relatively.

	 */

	/* no more than 50% of tags for async I/O */

	bfqd->async_depths[0][0] = max(nr_requests >> 1, 1U);

	/*

	 * no more than 75% of tags for sync writes (25% extra tags

	 * w.r.t. async I/O, to prevent async I/O from starving sync

	 * writes)

	 */

	bfqd->async_depths[0][1] = max((nr_requests * 3) >> 2, 1U);

	bfqd->async_depths[0][1] = async_depth;

	bfqd->async_depths[0][0] = max(async_depth * 2 / 3, 1U);

	bfqd->async_depths[1][1] = max(async_depth >> 1, 1U);

	bfqd->async_depths[1][0] = max(async_depth >> 2, 1U);



	/*

	 * In-word depths in case some bfq_queue is being weight-

	 * raised: leaving ~63% of tags for sync reads. This is the

	 * highest percentage for which, in our tests, application

	 * start-up times didn't suffer from any regression due to tag

	 * shortage.

	 * Due to cgroup qos, the allowed request for bfqq might be 1

	 */

	/* no more than ~18% of tags for async I/O */

	bfqd->async_depths[1][0] = max((nr_requests * 3) >> 4, 1U);

	/* no more than ~37% of tags for sync writes (~20% extra tags) */

	bfqd->async_depths[1][1] = max((nr_requests * 6) >> 4, 1U);



	blk_mq_set_min_shallow_depth(q, 1);

}
@@ -7365,6 +7355,7 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_queue *eq) 
	blk_queue_flag_set(QUEUE_FLAG_DISABLE_WBT_DEF, q);

	wbt_disable_default(q->disk);

	blk_stat_enable_accounting(q);

	q->async_depth = (q->nr_requests * 3) >> 2;



	return 0;