From: Jens Axboe axboe@kernel.dk
commit 26fed4ac4eab09c27fbae1859696cc38f0536407 upstream.
We used to sort the plug list if we had multiple queues before dispatching requests to the IO scheduler. This usually isn't needed, but for certain workloads that interleave requests to disks, it's a less efficient to process the plug list one-by-one if everything is interleaved.
Don't sort the list, but skip through it and flush out entries that have the same target at the same time.
Fixes: df87eb0fce8f ("block: get rid of plug list sorting") Reported-and-tested-by: Song Liu song@kernel.org Reviewed-by: Song Liu songliubraving@fb.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-mq.c | 59 +++++++++++++++++++++++++++------------------------------ 1 file changed, 28 insertions(+), 31 deletions(-)
--- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2561,13 +2561,36 @@ static void __blk_mq_flush_plug_list(str q->mq_ops->queue_rqs(&plug->mq_list); }
+static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched) +{ + struct blk_mq_hw_ctx *this_hctx = NULL; + struct blk_mq_ctx *this_ctx = NULL; + struct request *requeue_list = NULL; + unsigned int depth = 0; + LIST_HEAD(list); + + do { + struct request *rq = rq_list_pop(&plug->mq_list); + + if (!this_hctx) { + this_hctx = rq->mq_hctx; + this_ctx = rq->mq_ctx; + } else if (this_hctx != rq->mq_hctx || this_ctx != rq->mq_ctx) { + rq_list_add(&requeue_list, rq); + continue; + } + list_add_tail(&rq->queuelist, &list); + depth++; + } while (!rq_list_empty(plug->mq_list)); + + plug->mq_list = requeue_list; + trace_block_unplug(this_hctx->queue, depth, !from_sched); + blk_mq_sched_insert_requests(this_hctx, this_ctx, &list, from_sched); +} + void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule) { - struct blk_mq_hw_ctx *this_hctx; - struct blk_mq_ctx *this_ctx; struct request *rq; - unsigned int depth; - LIST_HEAD(list);
if (rq_list_empty(plug->mq_list)) return; @@ -2603,35 +2626,9 @@ void blk_mq_flush_plug_list(struct blk_p return; }
- this_hctx = NULL; - this_ctx = NULL; - depth = 0; do { - rq = rq_list_pop(&plug->mq_list); - - if (!this_hctx) { - this_hctx = rq->mq_hctx; - this_ctx = rq->mq_ctx; - } else if (this_hctx != rq->mq_hctx || this_ctx != rq->mq_ctx) { - trace_block_unplug(this_hctx->queue, depth, - !from_schedule); - blk_mq_sched_insert_requests(this_hctx, this_ctx, - &list, from_schedule); - depth = 0; - this_hctx = rq->mq_hctx; - this_ctx = rq->mq_ctx; - - } - - list_add(&rq->queuelist, &list); - depth++; + blk_mq_dispatch_plug_list(plug, from_schedule); } while (!rq_list_empty(plug->mq_list)); - - if (!list_empty(&list)) { - trace_block_unplug(this_hctx->queue, depth, !from_schedule); - blk_mq_sched_insert_requests(this_hctx, this_ctx, &list, - from_schedule); - } }
void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,