From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Damien Le Moal <dlemoal@kernel.org>,
	Bart Van Assche <bvanassche@acm.org>
Subject: [PATCH v3 1/2] block: Reorder the request allocation code in blk_mq_submit_bio()
Date: Wed, 18 Dec 2024 13:22:45 -0800	[thread overview]
Message-ID: <20241218212246.1073149-2-bvanassche@acm.org> (raw)
In-Reply-To: <20241218212246.1073149-1-bvanassche@acm.org>

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

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/blk-mq.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7ee21346a41e..8d2aab4d9ba9 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3102,12 +3102,12 @@ 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);

next prev parent reply	other threads:[~2024-12-18 21:23 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-18 21:22 [PATCH v3 0/2] Two blk_mq_submit_bio() patches Bart Van Assche
2024-12-18 21:22 ` Bart Van Assche [this message]
2024-12-19  5:33   ` [PATCH v3 1/2] block: Reorder the request allocation code in blk_mq_submit_bio() Christoph Hellwig
2025-01-14  0:43   ` Chaitanya Kulkarni
2024-12-18 21:22 ` [PATCH v3 2/2] blk-mq: Move more error handling into blk_mq_submit_bio() Bart Van Assche
2024-12-19  5:34   ` Christoph Hellwig
2025-01-14  0:46   ` Chaitanya Kulkarni
2025-01-14 17:13 ` [PATCH v3 0/2] Two blk_mq_submit_bio() patches Jens Axboe

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