Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 889fa31f authored by Chong Yuan's avatar Chong Yuan Committed by Jens Axboe
Browse files

blk-mq: reduce unnecessary software queue looping 



In flush_busy_ctxs() and blk_mq_hctx_has_pending(), regardless of how many
ctxs assigned to one hctx, they will all loop hctx->ctx_map.map_size
times. Here hctx->ctx_map.map_size is a const ALIGN(nr_cpu_ids, 8) / 8.
Especially, flush_busy_ctxs() is in hot code path. And it's unnecessary.
Change ->map_size to contain the actually mapped software queues, so we
only loop for as many iterations as we have to.

And remove cpumask setting and nr_ctx count in blk_mq_init_cpu_queues()
since they are all re-done in blk_mq_map_swqueue().
blk_mq_map_swqueue().

Signed-off-by: default avatarChong Yuan <chong.yuan@memblaze.com>
Reviewed-by: default avatarWenbo Wang <wenbo.wang@memblaze.com>

Updated by me for formatting and commenting.

Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent dc48e56d

block/blk-mq.c

+9 −4
Original line number Diff line number Diff line
@@ -1522,8 +1522,6 @@ static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node) 
	if (!bitmap->map)

		return -ENOMEM;



	bitmap->map_size = num_maps;



	total = nr_cpu_ids;

	for (i = 0; i < num_maps; i++) {

		bitmap->map[i].depth = min(total, bitmap->bits_per_word);
@@ -1764,8 +1762,6 @@ static void blk_mq_init_cpu_queues(struct request_queue *q, 
			continue;



		hctx = q->mq_ops->map_queue(q, i);

		cpumask_set_cpu(i, hctx->cpumask);

		hctx->nr_ctx++;



		/*

		 * Set local node, IFF we have more than one hw queue. If
@@ -1802,6 +1798,8 @@ static void blk_mq_map_swqueue(struct request_queue *q) 
	}



	queue_for_each_hw_ctx(q, hctx, i) {

		struct blk_mq_ctxmap *map = &hctx->ctx_map;



		/*

		 * If no software queues are mapped to this hardware queue,

		 * disable it and free the request entries.
@@ -1817,6 +1815,13 @@ static void blk_mq_map_swqueue(struct request_queue *q) 
			continue;

		}



		/*

		 * Set the map size to the number of mapped software queues.

		 * This is more accurate and more efficient than looping

		 * over all possibly mapped software queues.

		 */

		map->map_size = hctx->nr_ctx / map->bits_per_word;



		/*

		 * Initialize batch roundrobin counts

		 */