Re: [PATCH] kyber: introduce kyber_depth_updated()

[Jens Axboe <axboe@kernel.dk>]

On 1/22/21 2:06 AM, Yang Yang wrote:
> Hang occurs when user changes the scheduler queue depth, by writing to
> the 'nr_requests' sysfs file of that device.
> This patch introduces kyber_depth_updated(), so that kyber can update its
> internal state when queue depth changes.

Adding Omar.

> 
> Signed-off-by: Yang Yang <yang.yang@vivo.com>
> ---
>  block/kyber-iosched.c | 28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)
> 
> diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
> index dc89199bc8c6..b64f80d3eaf3 100644
> --- a/block/kyber-iosched.c
> +++ b/block/kyber-iosched.c
> @@ -353,19 +353,9 @@ 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;
>  
> @@ -400,9 +390,6 @@ 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:
> @@ -458,9 +445,18 @@ 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;
> +
> +	kqd->async_depth = tags->bitmap_tags->sb.depth * 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;
>  
> @@ -502,8 +498,7 @@ 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;
>  
> @@ -1022,6 +1017,7 @@ 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,
> 


-- 
Jens Axboe