Commit 44e41381 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

block: Reorder the request allocation code in blk_mq_submit_bio() 



Help the CPU branch predictor in case of a cache hit by handling the cache
hit scenario first.

Reviewed-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarChaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20241218212246.1073149-2-bvanassche@acm.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e7b94c5c

block/blk-mq.c

+3 −3
Original line number Diff line number Diff line
@@ -3125,12 +3125,12 @@ void blk_mq_submit_bio(struct bio *bio) 
		goto queue_exit;



new_request:

	if (!rq) {

	if (rq) {

		blk_mq_use_cached_rq(rq, plug, bio);

	} else {

		rq = blk_mq_get_new_requests(q, plug, bio, nr_segs);

		if (unlikely(!rq))

			goto queue_exit;

	} else {

		blk_mq_use_cached_rq(rq, plug, bio);

	}



	trace_block_getrq(bio);