From b2c5d16b72df1116f05c9be16a630ac939d34101 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 29 Nov 2018 10:03:42 -0700 Subject: [PATCH] blk-mq: use plug for devices that implement ->commits_rqs() If we have that hook, we know the driver handles bd->last == true in a smart fashion. If it does, even for multiple hardware queues, it's a good idea to flush batches of requests to the device, if we have batches of requests from the submitter. Reviewed-by: Ming Lei Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/blk-mq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 14e31e93a950..7dcef565dc0f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1945,7 +1945,11 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) /* bypass scheduler for flush rq */ blk_insert_flush(rq); blk_mq_run_hw_queue(data.hctx, true); - } else if (plug && q->nr_hw_queues == 1) { + } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs)) { + /* + * Use plugging if we have a ->commit_rqs() hook as well, as + * we know the driver uses bd->last in a smart fashion. + */ unsigned int request_count = plug->rq_count; struct request *last = NULL;