Commit ce5b009c authored by Jens Axboe's avatar Jens Axboe
Browse files

block: improve logic around when to sort a plug list 



Only do it if we have requests for multiple queues in the same
plug.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4e6db0f2

block/blk-core.c

+1 −0
Original line number Diff line number Diff line
@@ -1780,6 +1780,7 @@ void blk_start_plug(struct blk_plug *plug) 
	INIT_LIST_HEAD(&plug->mq_list);

	INIT_LIST_HEAD(&plug->cb_list);

	plug->rq_count = 0;

	plug->multiple_queues = false;



	/*

	 * Store ordering should not be needed here, since a potential

block/blk-mq.c

+18 −5
Original line number Diff line number Diff line
@@ -1677,6 +1677,7 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule) 
	list_splice_init(&plug->mq_list, &list);

	plug->rq_count = 0;



	if (plug->rq_count > 2 && plug->multiple_queues)

		list_sort(NULL, &list, plug_rq_cmp);



	this_q = NULL;
@@ -1866,6 +1867,20 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx, 
	}

}



static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)

{

	list_add_tail(&rq->queuelist, &plug->mq_list);

	plug->rq_count++;

	if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {

		struct request *tmp;



		tmp = list_first_entry(&plug->mq_list, struct request,

						queuelist);

		if (tmp->q != rq->q)

			plug->multiple_queues = true;

	}

}



static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)

{

	const int is_sync = op_is_sync(bio->bi_opf);
@@ -1932,8 +1947,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) 
			trace_block_plug(q);

		}



		list_add_tail(&rq->queuelist, &plug->mq_list);

		plug->rq_count++;

		blk_add_rq_to_plug(plug, rq);

	} else if (plug && !blk_queue_nomerges(q)) {

		blk_mq_bio_to_request(rq, bio);
@@ -1950,8 +1964,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) 
			list_del_init(&same_queue_rq->queuelist);

			plug->rq_count--;

		}

		list_add_tail(&rq->queuelist, &plug->mq_list);

		plug->rq_count++;

		blk_add_rq_to_plug(plug, rq);



		blk_mq_put_ctx(data.ctx);

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -1131,6 +1131,7 @@ struct blk_plug { 
	struct list_head mq_list; /* blk-mq requests */

	struct list_head cb_list; /* md requires an unplug callback */

	unsigned short rq_count;

	bool multiple_queues;

};

#define BLK_MAX_REQUEST_COUNT 16

#define BLK_PLUG_FLUSH_SIZE (128 * 1024)