linux-kernel - Re: [PATCH v3] mm/damon: Fix the timer always stays active

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Date:   Thu, 21 Apr 2022 08:48:06 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Hailong Tu <tuhailong@...il.com>
Cc:     akpm@...ux-foundation.org, sj@...nel.org,
        torvalds@...ux-foundation.org, gregkh@...gle.com,
        surenb@...gle.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, willy@...radead.org,
        tuhailong@...o.com, lichunpeng@...o.com, aaron.qiu@...o.com,
        fanguoze@...o.com
Subject: Re: [PATCH v3] mm/damon: Fix the timer always stays active

Hi Hailong,


On Thu, 21 Apr 2022 09:06:41 +0800 Hailong Tu <tuhailong@...il.com> wrote:

> The timer stays active even if the reclaim mechanism is never enabled.

I'd like to make it clear that this change is for DAMON_RECLAIM by making the
first part of the subject 'mm/damon/reclaim:', and adjusting above sentence.

> It is unnecessary overhead can be completely avoided by using module_param_call() for enabled flag.

Let's wrap the line at 75 columns
(https://docs.kernel.org/process/submitting-patches.html#the-canonical-patch-format).

> 
> Signed-off-by: Hailong Tu <tuhailong@...il.com>
> ---
>  mm/damon/reclaim.c | 19 +++++++++++++++++--
>  1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
> index e34c4d0c4d93..46505c501cd6 100644
> --- a/mm/damon/reclaim.c
> +++ b/mm/damon/reclaim.c
> @@ -28,7 +28,6 @@
>   * this.
>   */
>  static bool enabled __read_mostly;
> -module_param(enabled, bool, 0600);
>  
>  /*
>   * Time threshold for cold memory regions identification in microseconds.
> @@ -358,11 +357,27 @@ static void damon_reclaim_timer_fn(struct work_struct *work)
>  			enabled = last_enabled;
>  	}
>  
> -	schedule_delayed_work(&damon_reclaim_timer,
> +	if (enabled)
> +		schedule_delayed_work(&damon_reclaim_timer,
>  			msecs_to_jiffies(ENABLE_CHECK_INTERVAL_MS));
>  }
>  static DECLARE_DELAYED_WORK(damon_reclaim_timer, damon_reclaim_timer_fn);
>  
> +static int enabled_store(const char *val,
> +		const struct kernel_param *kp)
> +{
> +	int rc = param_set_bool(val, kp);
> +
> +	if (rc < 0)
> +		return rc;
> +
> +	if (enabled)
> +		schedule_delayed_work(&damon_reclaim_timer, 0);
> +
> +	return 0;
> +}
> +module_param_call(enabled, enabled_store, param_get_bool, &enabled, 0600);

module_param_call() is commented as obsolete.  Could we use module_param_cb()
instead as suggested by the comment?

> +
>  static int damon_reclaim_after_aggregation(struct damon_ctx *c)
>  {
>  	struct damos *s;
> -- 
> 2.25.1
> 


Thanks,
SJ