Commit 5ac83c64 authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe
Browse files

Revert "blk-mq, elevator: Count requests per hctx to improve performance" 



This reverts commit b445547e.

Since both mq-deadline and BFQ completely ignore hctx they are passed to
their dispatch function and dispatch whatever request they deem fit
checking whether any request for a particular hctx is queued is just
pointless since we'll very likely get a request from a different hctx
anyway. In the following commit we'll deal with lock contention in these
IO schedulers in presence of multiple HW queues in a different way.

Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2391d13e

block/bfq-iosched.c

+0 −5
Original line number Diff line number Diff line
@@ -4677,9 +4677,6 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx) 
{

	struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;



	if (!atomic_read(&hctx->elevator_queued))

		return false;



	/*

	 * Avoiding lock: a race on bfqd->busy_queues should cause at

	 * most a call to dispatch for nothing
@@ -5597,7 +5594,6 @@ static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx, 
		rq = list_first_entry(list, struct request, queuelist);

		list_del_init(&rq->queuelist);

		bfq_insert_request(hctx, rq, at_head);

		atomic_inc(&hctx->elevator_queued);

	}

}
@@ -5965,7 +5961,6 @@ static void bfq_finish_requeue_request(struct request *rq) 


		bfq_completed_request(bfqq, bfqd);

		bfq_finish_requeue_request_body(bfqq);

		atomic_dec(&rq->mq_hctx->elevator_queued);



		spin_unlock_irqrestore(&bfqd->lock, flags);

	} else {

block/blk-mq.c

+0 −1
Original line number Diff line number Diff line
@@ -2653,7 +2653,6 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set, 
		goto free_hctx;



	atomic_set(&hctx->nr_active, 0);

	atomic_set(&hctx->elevator_queued, 0);

	if (node == NUMA_NO_NODE)

		node = set->numa_node;

	hctx->numa_node = node;

block/mq-deadline.c

+0 −6
Original line number Diff line number Diff line
@@ -386,8 +386,6 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) 
	spin_lock(&dd->lock);

	rq = __dd_dispatch_request(dd);

	spin_unlock(&dd->lock);

	if (rq)

		atomic_dec(&rq->mq_hctx->elevator_queued);



	return rq;

}
@@ -535,7 +533,6 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, 
		rq = list_first_entry(list, struct request, queuelist);

		list_del_init(&rq->queuelist);

		dd_insert_request(hctx, rq, at_head);

		atomic_inc(&hctx->elevator_queued);

	}

	spin_unlock(&dd->lock);

}
@@ -582,9 +579,6 @@ static bool dd_has_work(struct blk_mq_hw_ctx *hctx) 
{

	struct deadline_data *dd = hctx->queue->elevator->elevator_data;



	if (!atomic_read(&hctx->elevator_queued))

		return false;



	return !list_empty_careful(&dd->dispatch) ||

		!list_empty_careful(&dd->fifo_list[0]) ||

		!list_empty_careful(&dd->fifo_list[1]);

include/linux/blk-mq.h

+0 −4
Original line number Diff line number Diff line
@@ -140,10 +140,6 @@ struct blk_mq_hw_ctx { 
	 * shared across request queues.

	 */

	atomic_t		nr_active;

	/**

	 * @elevator_queued: Number of queued requests on hctx.

	 */

	atomic_t                elevator_queued;



	/** @cpuhp_online: List to store request if CPU is going to die */

	struct hlist_node	cpuhp_online;