Do it for the nr_hw_queues == 1 case, but only do it for the multi queue case if we have requests for multiple devices in the plug.
Signed-off-by: Jens Axboe <[email protected]> --- block/blk-core.c | 1 + block/blk-mq.c | 7 +++++-- include/linux/blkdev.h | 1 + 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index be9233400314..c9758d185357 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1780,6 +1780,7 @@ void blk_start_plug(struct blk_plug *plug) INIT_LIST_HEAD(&plug->mq_list); INIT_LIST_HEAD(&plug->cb_list); plug->rq_count = 0; + plug->do_sort = false; /* * Store ordering should not be needed here, since a potential diff --git a/block/blk-mq.c b/block/blk-mq.c index 99c66823d52f..6a249bf6ed00 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1678,7 +1678,8 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule) list_splice_init(&plug->mq_list, &list); plug->rq_count = 0; - list_sort(NULL, &list, plug_rq_cmp); + if (plug->do_sort) + list_sort(NULL, &list, plug_rq_cmp); this_q = NULL; this_hctx = NULL; @@ -1935,6 +1936,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) list_add_tail(&rq->queuelist, &plug->mq_list); plug->rq_count++; + plug->do_sort = true; } else if (plug && !blk_queue_nomerges(q)) { blk_mq_bio_to_request(rq, bio); @@ -1958,7 +1960,8 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) data.hctx = same_queue_rq->mq_hctx; blk_mq_try_issue_directly(data.hctx, same_queue_rq, &cookie); - } + } else if (plug->rq_count > 1) + plug->do_sort = true; } else if ((q->nr_hw_queues > 1 && is_sync) || (!q->elevator && !data.hctx->dispatch_busy)) { blk_mq_put_ctx(data.ctx); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 02732cae6080..b6d0b33feee7 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1131,6 +1131,7 @@ struct blk_plug { struct list_head mq_list; /* blk-mq requests */ struct list_head cb_list; /* md requires an unplug callback */ unsigned short rq_count; + bool do_sort; }; #define BLK_MAX_REQUEST_COUNT 16 #define BLK_PLUG_FLUSH_SIZE (128 * 1024) -- 2.17.1
