| From 15f96904b2d81ce03dceaa7be9c4b33e7cd4d4c2 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 7 Sep 2021 16:03:38 -0700 |
| Subject: blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for |
| multiple_queues |
| |
| 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 9d4fdc2be88a..9c64f0025a56 100644 |
| --- a/block/blk-mq.c |
| +++ b/block/blk-mq.c |
| @@ -2135,6 +2135,18 @@ 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. |
| @@ -2231,7 +2243,7 @@ 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 |
| |
