From ab42f35d9cb5ac49b5a2a11f940e74f58f207280 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 26 May 2017 19:53:19 +0800 Subject: [PATCH] blk-mq: merge bio into sw queue before plugging Before blk-mq is introduced, I/O is merged to elevator before being putted into plug queue, but blk-mq changed the order and makes merging to sw queue basically impossible. Then it is observed that throughput of sequential I/O is degraded about 10%~20% on virtio-blk in the test[1] if mq-deadline isn't used. This patch moves the bio merging per sw queue before plugging, like what blk_queue_bio() does, and the performance regression is fixed under this situation. [1]. test script: sudo fio --direct=1 --size=128G --bsrange=4k-4k --runtime=40 --numjobs=16 --ioengine=libaio --iodepth=64 --group_reporting=1 --filename=/dev/vdb --name=virtio_blk-test-$RW --rw=$RW --output-format=json RW=read or write Reviewed-by: Christoph Hellwig Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- block/blk-mq.c | 48 ++++++++++++++++++++++++++---------------------- 1 file changed, 26 insertions(+), 22 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index f2224ffd225d..fd8244cf50a4 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1427,30 +1427,30 @@ static inline bool hctx_allow_merges(struct blk_mq_hw_ctx *hctx) !blk_queue_nomerges(hctx->queue); } -static inline bool blk_mq_merge_queue_io(struct blk_mq_hw_ctx *hctx, - struct blk_mq_ctx *ctx, - struct request *rq, struct bio *bio) +/* attempt to merge bio into current sw queue */ +static inline bool blk_mq_merge_bio(struct request_queue *q, struct bio *bio) { - if (!hctx_allow_merges(hctx) || !bio_mergeable(bio)) { - blk_mq_bio_to_request(rq, bio); - spin_lock(&ctx->lock); -insert_rq: - __blk_mq_insert_request(hctx, rq, false); - spin_unlock(&ctx->lock); - return false; - } else { - struct request_queue *q = hctx->queue; + bool ret = false; + struct blk_mq_ctx *ctx = blk_mq_get_ctx(q); + struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu); + if (hctx_allow_merges(hctx) && bio_mergeable(bio)) { spin_lock(&ctx->lock); - if (!blk_mq_attempt_merge(q, ctx, bio)) { - blk_mq_bio_to_request(rq, bio); - goto insert_rq; - } - + ret = blk_mq_attempt_merge(q, ctx, bio); spin_unlock(&ctx->lock); - __blk_mq_finish_request(hctx, ctx, rq); - return true; } + + blk_mq_put_ctx(ctx); + return ret; +} + +static inline void blk_mq_queue_io(struct blk_mq_hw_ctx *hctx, + struct blk_mq_ctx *ctx, + struct request *rq) +{ + spin_lock(&ctx->lock); + __blk_mq_insert_request(hctx, rq, false); + spin_unlock(&ctx->lock); } static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq) @@ -1549,6 +1549,9 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) if (blk_mq_sched_bio_merge(q, bio)) return BLK_QC_T_NONE; + if (blk_mq_merge_bio(q, bio)) + return BLK_QC_T_NONE; + wb_acct = wbt_wait(q->rq_wb, bio, NULL); trace_block_getrq(q, bio, bio->bi_opf); @@ -1630,11 +1633,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) blk_mq_put_ctx(data.ctx); blk_mq_bio_to_request(rq, bio); blk_mq_sched_insert_request(rq, false, true, true, true); - } else if (!blk_mq_merge_queue_io(data.hctx, data.ctx, rq, bio)) { + } else { blk_mq_put_ctx(data.ctx); + blk_mq_bio_to_request(rq, bio); + blk_mq_queue_io(data.hctx, data.ctx, rq); blk_mq_run_hw_queue(data.hctx, true); - } else - blk_mq_put_ctx(data.ctx); + } return cookie; } -- 2.30.2