diff options
| author | Kashyap Desai <kashyap.desai@broadcom.com> | 2020-08-19 23:20:28 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-09-03 15:20:47 -0600 |
| commit | b445547ec1bbd3e7bf4b1c142550942f70527d95 (patch) | |
| tree | 452adb8f18969cd32966206e046632f1d7ff9b44 /block | |
| parent | f1b49fdc1c64db110aa1315831e5fe0f8599fa56 (diff) | |
| download | linux-b445547ec1bbd3e7bf4b1c142550942f70527d95.tar.bz2 | |
blk-mq, elevator: Count requests per hctx to improve performance
High CPU utilization on "native_queued_spin_lock_slowpath" due to lock
contention is possible for mq-deadline and bfq IO schedulers
when nr_hw_queues is more than one.
It is because kblockd work queue can submit IO from all online CPUs
(through blk_mq_run_hw_queues()) even though only one hctx has pending
commands.
The elevator callback .has_work for mq-deadline and bfq scheduler considers
pending work if there are any IOs on request queue but it does not account
hctx context.
Add a per-hctx 'elevator_queued' count to the hctx to avoid triggering
the elevator even though there are no requests queued.
[jpg: Relocated atomic_dec() in dd_dispatch_request(), update commit message per Kashyap]
Signed-off-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: John Garry <john.garry@huawei.com>
Tested-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/bfq-iosched.c | 5 | ||||
| -rw-r--r-- | block/blk-mq.c | 1 | ||||
| -rw-r--r-- | block/mq-deadline.c | 6 |
3 files changed, 12 insertions, 0 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 418ffd4b5552..a251b80d8ee5 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -4640,6 +4640,9 @@ 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 @@ -5554,6 +5557,7 @@ 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); } } @@ -5933,6 +5937,7 @@ 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 eff9d987f85b..4abb71459f94 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2660,6 +2660,7 @@ 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 b57470e154c8..800ac902809b 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -386,6 +386,8 @@ 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; } @@ -533,6 +535,7 @@ 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); } @@ -579,6 +582,9 @@ 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]); |