From: wenxiong@linux.ibm.com
To: linux-block@vger.kernel.org, axboe@kernel.dk
Cc: tom.leiming@gmail.com, yukuai@fygo.io, stable@vger.kernel.org,
	wenxiong@us.ibm.com, Wen Xiong <wenxiong@linux.ibm.com>
Subject: [PATCH V2]block: Remove redundant plug in __submit_bio()
Date: Tue, 16 Jun 2026 10:31:21 -0400	[thread overview]
Message-ID: <20260616143121.878021-1-wenxiong@linux.ibm.com> (raw)

From: Wen Xiong <wenxiong@linux.ibm.com>

The patch removes the automatic plug/unplug operations from __submit_bio()
that were added to cache nsecs time when no explicit plug is used.

The plug mechanism is most effective when batching multiple I/O
operations together. Creating a plug for every bio submission
provides minimal benefit while adding function call overhead and
stack usage for every I/O operation.

Below is performance comparison with the latest upstream kernel.

Iotype  qd nj  rmix  mpstat busy  mpstat busy without plug
Randrw  1  20  100       53%                 24%
Randrw  1  40  100       70%                 24%
Randrw  1  20  70        40%                 24%
Randrw  1  40  70        60%                 26%
Randrw  1  20  0         14%                 6%
Randrw  1  40  0         20%                 7%

Fixes: 060406c61c7c ("block: add plug while submitting IO")
Signed-off-by: Wen Xiong <wenxiong@linux.ibm.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
---
 block/blk-core.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 73a41df98c9a..365641266c9e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -669,11 +669,6 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
 
 static void __submit_bio(struct bio *bio)
 {
-	/* If plug is not used, add new plug here to cache nsecs time. */
-	struct blk_plug plug;
-
-	blk_start_plug(&plug);
-
 	if (!bdev_test_flag(bio->bi_bdev, BD_HAS_SUBMIT_BIO)) {
 		blk_mq_submit_bio(bio);
 	} else if (likely(bio_queue_enter(bio) == 0)) {
@@ -686,8 +681,6 @@ static void __submit_bio(struct bio *bio)
 			disk->fops->submit_bio(bio);
 		blk_queue_exit(disk->queue);
 	}
-
-	blk_finish_plug(&plug);
 }
 
 /*
-- 
2.52.0

next             reply	other threads:[~2026-06-16 14:31 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-16 14:31 wenxiong [this message]
2026-06-16 16:08 ` [PATCH V2]block: Remove redundant plug in __submit_bio() Jens Axboe

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