[PATCH v3] mm/damon: Fix the timer always stays active

[PATCH v3] mm/damon: Fix the timer always stays active

[Hailong Tu]

The timer stays active even if the reclaim mechanism is never enabled.
It is unnecessary overhead can be completely avoided by using module_param_call() for enabled flag.

Signed-off-by: Hailong Tu <tuhailong@gmail.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);
+
 static int damon_reclaim_after_aggregation(struct damon_ctx *c)
 {
 	struct damos *s;
-- 
2.25.1

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

[SeongJae Park]

Hi Hailong,


On Thu, 21 Apr 2022 09:06:41 +0800 Hailong Tu <tuhailong@gmail.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@gmail.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