On 2019/09/27 0:25, Ming Lei wrote:
> Some HDD drive may expose multiple hw queue, such as MegraRaid, so
> still apply the normal plugging for such devices because sequential IO
> may benefit a lot from plug merging.
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Damien Le Moal <damien.lemoal@xxxxxxx>
> Cc: Dave Chinner <dchinner@xxxxxxxxxx>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> ---
> 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 d7aed6518e62..969dfe02fa7c 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1983,10 +1983,14 @@ 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 || q->mq_ops->commit_rqs)) {
> + } else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs ||
> + !blk_queue_nonrot(q))) {
> /*
> * Use plugging if we have a ->commit_rqs() hook as well, as
> * we know the driver uses bd->last in a smart fashion.
> + *
> + * Use normal plugging if this disk is slow HDD, as sequential
> + * IO may benefit a lot from plug merging.
> */
> unsigned int request_count = plug->rq_count;
> struct request *last = NULL;
>
Cc stable needed ?
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
--
Damien Le Moal
Western Digital Research
