[PATCH v2 2/2] blk-mq: Add a polling specific stats function

[Jens Axboe]

On 04/05/2017 11:39 AM, sbates at raithlin.com wrote:
> @@ -42,6 +42,33 @@ static LIST_HEAD(all_q_list);
>  static void blk_mq_poll_stats_start(struct request_queue *q);
>  static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);
>  
> +static int blk_mq_poll_stats_bkt(const struct request *rq)
> +{
> +	int dir, bytes;
> +
> +	dir = blk_stat_rq_ddir(rq);
> +	bytes = blk_rq_bytes(rq);
> +
> +	if (bytes <= 512)
> +		return dir;
> +	else if (bytes <= 4096)
> +		return dir + 2;
> +	else if (bytes <= 8192)
> +		return dir + 4;
> +	else if (bytes <= 16384)
> +		return dir + 6;
> +	else if (bytes <= 32768)
> +		return dir + 8;
> +	else if (bytes <= 65536)
> +		return dir + 10;
> +	else
> +		return dir + 12;

Why not just have 8 buckets, and make it:

	bucket = ddir + ilog2(bytes) - 9;

and cap it at MAX_BUCKET (8) and put all those above into the top
bucket.

-- 
Jens Axboe