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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Song Liu <songliubraving@fb.com>,
	Marcin Wanat <marcin.wanat@gmail.com>,
	Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>,
	linux-block@vger.kernel.org
Subject: [PATCH AUTOSEL 5.10 6/8] blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for multiple_queues
Date: Thu, 16 Sep 2021 22:34:31 -0400	[thread overview]
Message-ID: <20210917023437.816574-6-sashal@kernel.org> (raw)
In-Reply-To: <20210917023437.816574-1-sashal@kernel.org>

From: Song Liu <songliubraving@fb.com>

[ Upstream commit 7f2a6a69f7ced6db8220298e0497cf60482a9d4b ]

Limiting number of request to BLK_MAX_REQUEST_COUNT at blk_plug hurts
performance for large md arrays. [1] shows resync speed of md array drops
for md array with more than 16 HDDs.

Fix this by allowing more request at plug queue. The multiple_queue flag
is used to only apply higher limit to multiple queue cases.

[1] https://lore.kernel.org/linux-raid/CAFDAVznS71BXW8Jxv6k9dXc2iR3ysX3iZRBww_rzA8WifBFxGg@mail.gmail.com/
Tested-by: Marcin Wanat <marcin.wanat@gmail.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-mq.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9e3fedbaa644..6dcb86c1c985 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2109,6 +2109,18 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
 	}
 }
 
+/*
+ * Allow 4x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
+ * queues. This is important for md arrays to benefit from merging
+ * requests.
+ */
+static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
+{
+	if (plug->multiple_queues)
+		return BLK_MAX_REQUEST_COUNT * 4;
+	return BLK_MAX_REQUEST_COUNT;
+}
+
 /**
  * blk_mq_submit_bio - Create and send a request to block device.
  * @bio: Bio pointer.
@@ -2202,7 +2214,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
 		else
 			last = list_entry_rq(plug->mq_list.prev);
 
-		if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
+		if (request_count >= blk_plug_max_rq_count(plug) || (last &&
 		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
 			blk_flush_plug_list(plug, false);
 			trace_block_plug(q);
-- 
2.30.2


      parent reply	other threads:[~2021-09-17  2:35 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210917023437.816574-1-sashal@kernel.org>
2021-09-17  2:34 ` [PATCH AUTOSEL 5.10 5/8] blk-throttle: fix UAF by deleteing timer in blk_throtl_exit() Sasha Levin
2021-09-17  2:34 ` Sasha Levin [this message]

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