[PATCH 1/2] Revert "blk-mq, elevator: Count requests per hctx to improve performance"
From: Jan Kara <jack@suse.cz>
Date: 2021-01-06 10:25:20
Subsystem:
bfq i/o scheduler, block layer, the rest · Maintainers:
Yu Kuai, Jens Axboe, Linus Torvalds
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@suse.cz> --- 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