From: Yu Kuai The default limits is unchanged, and user can configure async_depth now. Signed-off-by: Yu Kuai --- block/bfq-iosched.c | 43 +++++++++++++++++-------------------------- 1 file changed, 17 insertions(+), 26 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 704900675949..3350c9b22eb4 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -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<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); } @@ -7360,6 +7350,7 @@ 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; -- 2.39.2