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blk-mq: use plug for devices that implement ->commits_rqs()

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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 <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-11-29 10:03:42 -07:00
parent be94f058f2
commit b2c5d16b72
1 changed files with 5 additions and 1 deletions
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6
block/blk-mq.c
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@ -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;