Re: [PATCH 2/2] blk-wbt: export internal state via debugfs

[Bart Van Assche <bvanassche@acm.org>]

On Fri, 2018-12-14 at 19:39 +0800, Ming Lei wrote:
> This information is helpful to either investigate issues, or understand
> wbt's internal behaviour.
> 
> Cc: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Josef Bacik <josef@toxicpanda.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  block/blk-wbt.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 91 insertions(+)
> 
> diff --git a/block/blk-wbt.c b/block/blk-wbt.c
> index 463e4eb80287..2684bf2d112f 100644
> --- a/block/blk-wbt.c
> +++ b/block/blk-wbt.c
> @@ -715,6 +715,94 @@ void wbt_disable_default(struct request_queue *q)
>  }
>  EXPORT_SYMBOL_GPL(wbt_disable_default);
>  
> +#ifdef CONFIG_BLK_DEBUG_FS
> +static int wbt_curr_window_show(void *data, struct seq_file *m)
> +{
> +	struct rq_qos *rqos = data;
> +	struct rq_wb *rwb = RQWB(rqos);
> +
> +	seq_printf(m, "%llu ns\n", rwb->cur_win_nsec);
> +	return 0;
> +}

Please consider to embed the unit ("ns") in the attribute name instead of
in the attribute value. That will make it easier to process this attribute
in developer debug scripts.

> +static int wbt_min_latency_show(void *data, struct seq_file *m)
> +{
> +	struct rq_qos *rqos = data;
> +	struct rq_wb *rwb = RQWB(rqos);
> +
> +	seq_printf(m, "%luns\n", rwb->min_lat_nsec);
> +	return 0;
> +}

Same comment here about the unit.

> +static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = {
> +	{"curr_window", 0400, wbt_curr_window_show},
> +	{"enable_state", 0400, wbt_enable_state_show},

How about using "enabled" instead of "enable_state"?

Thanks,

Bart.