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Message-Id: <20210924124336.327864479@linuxfoundation.org>
Date: Fri, 24 Sep 2021 14:45:00 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Marcin Wanat <marcin.wanat@...il.com>,
Song Liu <songliubraving@...com>, Jens Axboe <axboe@...nel.dk>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 60/63] blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for multiple_queues
From: Song Liu <songliubraving@...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@...il.com>
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.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);
--
2.33.0
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