blk-mq: allow 4x BLK_MAX_REQUEST_COUNT at blk_plug for multiple_queues
[ 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>
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@ -2135,6 +2135,18 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
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}
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}
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}
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}
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/*
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* Allow 4x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
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* queues. This is important for md arrays to benefit from merging
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* requests.
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*/
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static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
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{
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if (plug->multiple_queues)
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return BLK_MAX_REQUEST_COUNT * 4;
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return BLK_MAX_REQUEST_COUNT;
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}
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/**
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/**
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* blk_mq_submit_bio - Create and send a request to block device.
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* blk_mq_submit_bio - Create and send a request to block device.
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* @bio: Bio pointer.
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* @bio: Bio pointer.
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@ -2231,7 +2243,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
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else
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else
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last = list_entry_rq(plug->mq_list.prev);
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last = list_entry_rq(plug->mq_list.prev);
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if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
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if (request_count >= blk_plug_max_rq_count(plug) || (last &&
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blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
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blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
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blk_flush_plug_list(plug, false);
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blk_flush_plug_list(plug, false);
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trace_block_plug(q);
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trace_block_plug(q);
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