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Revert "blk-mq, elevator: Count requests per hctx to improve performance"

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This reverts commit b445547ec1.

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@suse.cz>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jan Kara 2021-01-11 17:47:16 +01:00 • committed by Jens Axboe
parent 2391d13ed4
commit 5ac83c644f
4 changed files with 0 additions and 16 deletions
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5
block/bfq-iosched.c
View file

@ -4677,9 +4677,6 @@ static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
{ {
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data; 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 * Avoiding lock: a race on bfqd->busy_queues should cause at
* most a call to dispatch for nothing * most a call to dispatch for nothing
@ -5597,7 +5594,6 @@ static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
rq = list_first_entry(list, struct request, queuelist); rq = list_first_entry(list, struct request, queuelist);
list_del_init(&rq->queuelist); list_del_init(&rq->queuelist);
bfq_insert_request(hctx, rq, at_head); bfq_insert_request(hctx, rq, at_head);
atomic_inc(&hctx->elevator_queued);
} }
} }
@ -5965,7 +5961,6 @@ static void bfq_finish_requeue_request(struct request *rq)
bfq_completed_request(bfqq, bfqd); bfq_completed_request(bfqq, bfqd);
bfq_finish_requeue_request_body(bfqq); bfq_finish_requeue_request_body(bfqq);
atomic_dec(&rq->mq_hctx->elevator_queued);
spin_unlock_irqrestore(&bfqd->lock, flags); spin_unlock_irqrestore(&bfqd->lock, flags);
} else { } else {

1
block/blk-mq.c
View file

@ -2653,7 +2653,6 @@ blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
goto free_hctx; goto free_hctx;
atomic_set(&hctx->nr_active, 0); atomic_set(&hctx->nr_active, 0);
atomic_set(&hctx->elevator_queued, 0);
if (node == NUMA_NO_NODE) if (node == NUMA_NO_NODE)
node = set->numa_node; node = set->numa_node;
hctx->numa_node = node; hctx->numa_node = node;

6
block/mq-deadline.c
View file

@ -386,8 +386,6 @@ static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)
spin_lock(&dd->lock); spin_lock(&dd->lock);
rq = __dd_dispatch_request(dd); rq = __dd_dispatch_request(dd);
spin_unlock(&dd->lock); spin_unlock(&dd->lock);
if (rq)
atomic_dec(&rq->mq_hctx->elevator_queued);
return rq; 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); rq = list_first_entry(list, struct request, queuelist);
list_del_init(&rq->queuelist); list_del_init(&rq->queuelist);
dd_insert_request(hctx, rq, at_head); dd_insert_request(hctx, rq, at_head);
atomic_inc(&hctx->elevator_queued);
} }
spin_unlock(&dd->lock); 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; struct deadline_data *dd = hctx->queue->elevator->elevator_data;
if (!atomic_read(&hctx->elevator_queued))
return false;
return !list_empty_careful(&dd->dispatch) || return !list_empty_careful(&dd->dispatch) ||
!list_empty_careful(&dd->fifo_list[0]) || !list_empty_careful(&dd->fifo_list[0]) ||
!list_empty_careful(&dd->fifo_list[1]); !list_empty_careful(&dd->fifo_list[1]);

4
include/linux/blk-mq.h
View file

@ -140,10 +140,6 @@ struct blk_mq_hw_ctx {
* shared across request queues. * shared across request queues.
*/ */
atomic_t nr_active; 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 */ /** @cpuhp_online: List to store request if CPU is going to die */
struct hlist_node cpuhp_online; struct hlist_node cpuhp_online;