On Mon, Jan 11, 2021 at 05:47:16PM +0100, Jan Kara wrote:
> This reverts commit b445547ec1bbd3e7bf4b1c142550942f70527d95.
>
> Since both mq-deadline and BFQ completely ignore hctx they are passed to
> their dispatch function and dispatch whatever request they deem fit
> checking whether any request for a particular hctx is queued is just
> pointless since we'll very likely get a request from a different hctx
> anyway. In the following commit we'll deal with lock contention in these
> IO schedulers in presence of multiple HW queues in a different way.
>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> block/bfq-iosched.c | 5 -----
> block/blk-mq.c | 1 -
> block/mq-deadline.c | 6 ------
> include/linux/blk-mq.h | 4 ----
> 4 files changed, 16 deletions(-)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 9e81d1052091..a99dfaa75a8c 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -4640,9 +4640,6 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
> {
> struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
>
> - if (!atomic_read(&hctx->elevator_queued))
> - return false;
> -
> /*
> * Avoiding lock: a race on bfqd->busy_queues should cause at
> * most a call to dispatch for nothing
> @@ -5557,7 +5554,6 @@ static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
> rq = list_first_entry(list, struct request, queuelist);
> list_del_init(&rq->queuelist);
> bfq_insert_request(hctx, rq, at_head);
> - atomic_inc(&hctx->elevator_queued);
> }
> }
>
> @@ -5925,7 +5921,6 @@ static void bfq_finish_requeue_request(struct request *rq)
>
> bfq_completed_request(bfqq, bfqd);
> bfq_finish_requeue_request_body(bfqq);
> - atomic_dec(&rq->mq_hctx->elevator_queued);
>
> spin_unlock_irqrestore(&bfqd->lock, flags);
> } else {
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index f285a9123a8b..57f3482b2c26 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2653,7 +2653,6 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
> goto free_hctx;
>
> atomic_set(&hctx->nr_active, 0);
> - atomic_set(&hctx->elevator_queued, 0);
> if (node == NUMA_NO_NODE)
> node = set->numa_node;
> hctx->numa_node = node;
> diff --git a/block/mq-deadline.c b/block/mq-deadline.c
> index 800ac902809b..b57470e154c8 100644
> --- a/block/mq-deadline.c
> +++ b/block/mq-deadline.c
> @@ -386,8 +386,6 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
> spin_lock(&dd->lock);
> rq = __dd_dispatch_request(dd);
> spin_unlock(&dd->lock);
> - if (rq)
> - atomic_dec(&rq->mq_hctx->elevator_queued);
>
> return rq;
> }
> @@ -535,7 +533,6 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,
> rq = list_first_entry(list, struct request, queuelist);
> list_del_init(&rq->queuelist);
> dd_insert_request(hctx, rq, at_head);
> - atomic_inc(&hctx->elevator_queued);
> }
> spin_unlock(&dd->lock);
> }
> @@ -582,9 +579,6 @@ static bool dd_has_work(struct blk_mq_hw_ctx *hctx)
> {
> struct deadline_data *dd = hctx->queue->elevator->elevator_data;
>
> - if (!atomic_read(&hctx->elevator_queued))
> - return false;
> -
> return !list_empty_careful(&dd->dispatch) ||
> !list_empty_careful(&dd->fifo_list[0]) ||
> !list_empty_careful(&dd->fifo_list[1]);
> diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
> index d705b174d346..b4b9604bbfd7 100644
> --- a/include/linux/blk-mq.h
> +++ b/include/linux/blk-mq.h
> @@ -140,10 +140,6 @@ struct blk_mq_hw_ctx {
> * shared across request queues.
> */
> atomic_t nr_active;
> - /**
> - * @elevator_queued: Number of queued requests on hctx.
> - */
> - atomic_t elevator_queued;
>
> /** @cpuhp_online: List to store request if CPU is going to die */
> struct hlist_node cpuhp_online;
> --
> 2.26.2
>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
--
Ming
