Commit ffa772cf authored by Yang Yang's avatar Yang Yang Committed by Jens Axboe
Browse files

kyber: introduce kyber_depth_updated() 



Hang occurs when user changes the scheduler queue depth, by writing to
the 'nr_requests' sysfs file of that device.

The details of the environment that we found the problem are as follows:
  an eMMC block device
  total driver tags: 16
  default queue_depth: 32
  kqd->async_depth initialized in kyber_init_sched() with queue_depth=32

Then we change queue_depth to 256, by writing to the 'nr_requests' sysfs
file. But kqd->async_depth don't be updated after queue_depth changes.
Now the value of async depth is too small for queue_depth=256, this may
cause hang.

This patch introduces kyber_depth_updated(), so that kyber can update
async depth when queue depth changes.

Signed-off-by: default avatarYang Yang <yang.yang@vivo.com>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4ceddce5

block/kyber-iosched.c

+13 −16
Original line number Diff line number Diff line
@@ -355,19 +355,9 @@ static void kyber_timer_fn(struct timer_list *t) 
	}

}



static unsigned int kyber_sched_tags_shift(struct request_queue *q)

{

	/*

	 * All of the hardware queues have the same depth, so we can just grab

	 * the shift of the first one.

	 */

	return q->queue_hw_ctx[0]->sched_tags->bitmap_tags->sb.shift;

}



static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)

{

	struct kyber_queue_data *kqd;

	unsigned int shift;

	int ret = -ENOMEM;

	int i;
@@ -402,9 +392,6 @@ static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q) 
		kqd->latency_targets[i] = kyber_latency_targets[i];

	}



	shift = kyber_sched_tags_shift(q);

	kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;



	return kqd;



err_buckets:
@@ -460,9 +447,19 @@ static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq) 
		INIT_LIST_HEAD(&kcq->rq_list[i]);

}



static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)

static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)

{

	struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;

	struct blk_mq_tags *tags = hctx->sched_tags;

	unsigned int shift = tags->bitmap_tags->sb.shift;



	kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;



	sbitmap_queue_min_shallow_depth(tags->bitmap_tags, kqd->async_depth);

}



static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)

{

	struct kyber_hctx_data *khd;

	int i;
@@ -504,8 +501,7 @@ static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx) 
	khd->batching = 0;



	hctx->sched_data = khd;

	sbitmap_queue_min_shallow_depth(hctx->sched_tags->bitmap_tags,

					kqd->async_depth);

	kyber_depth_updated(hctx);



	return 0;
@@ -1024,6 +1020,7 @@ static struct elevator_type kyber_sched = { 
		.completed_request = kyber_completed_request,

		.dispatch_request = kyber_dispatch_request,

		.has_work = kyber_has_work,

		.depth_updated = kyber_depth_updated,

	},

#ifdef CONFIG_BLK_DEBUG_FS

	.queue_debugfs_attrs = kyber_queue_debugfs_attrs,