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authorMing Lei <ming.lei@redhat.com>2017-05-26 14:53:19 +0300
committerJens Axboe <axboe@fb.com>2017-05-26 23:12:03 +0300
commitab42f35d9cb5ac49b5a2a11f940e74f58f207280 (patch)
treed3fedd45516727f64f0efa1f494755cbabd8a6cc /block
parentcdbe0206783b4e86abb0150303f137e448b5e531 (diff)
downloadlinux-ab42f35d9cb5ac49b5a2a11f940e74f58f207280.tar.xz
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 <hch@lst.de> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c48
1 files 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;
}