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From:   SeongJae Park <sj@kernel.org>
To:     xiakaixu1987@gmail.com
Cc:     sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Kaixu Xia <kaixuxia@tencent.com>
Subject: Re: [PATCH] mm/damon: deduplicate damon_{reclaim,lru_sort}_apply_parameters()
Date:   Mon, 19 Sep 2022 16:56:04 +0000
Message-Id: <20220919165604.61177-1-sj@kernel.org>
In-Reply-To: <1663568889-17634-1-git-send-email-kaixuxia@tencent.com>
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Hi Kaixu,

On Mon, 19 Sep 2022 14:28:09 +0800 xiakaixu1987@gmail.com wrote:

> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> The bodies of damon_{reclaim,lru_sort}_apply_parameters() contain
> duplicates.

Good finding!

> This commit add a common function
> damon_set_regions_from_system_ram() to removes the duplicates.
> 
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> ---
>  include/linux/damon.h |  3 ++-
>  mm/damon/core.c       | 20 +++++++++++++++++++-
>  mm/damon/lru_sort.c   | 13 +++----------
>  mm/damon/reclaim.c    | 13 +++----------
>  4 files changed, 27 insertions(+), 22 deletions(-)
> 
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index e7808a84675f..2fd05568ef45 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -557,7 +557,8 @@ static inline bool damon_target_has_pid(const struct damon_ctx *ctx)
>  int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive);
>  int damon_stop(struct damon_ctx **ctxs, int nr_ctxs);
>  
> -bool damon_find_biggest_system_ram(unsigned long *start, unsigned long *end);
> +int damon_set_regions_from_system_ram(struct damon_target *t,
> +				unsigned long *start, unsigned long *end);
>  
>  #endif	/* CONFIG_DAMON */
>  
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 9c80c6eb00c2..d967b2805a53 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1245,7 +1245,8 @@ static int walk_system_ram(struct resource *res, void *arg)
>   * Find biggest 'System RAM' resource and store its start and end address in
>   * @start and @end, respectively.  If no System RAM is found, returns false.
>   */
> -bool damon_find_biggest_system_ram(unsigned long *start, unsigned long *end)
> +static bool damon_find_biggest_system_ram(unsigned long *start,
> +						unsigned long *end)
>  
>  {
>  	struct damon_system_ram_region arg = {};
> @@ -1259,6 +1260,23 @@ bool damon_find_biggest_system_ram(unsigned long *start, unsigned long *end)
>  	return true;
>  }
>  
> +int damon_set_regions_from_system_ram(struct damon_target *t,
> +			unsigned long *start, unsigned long *end)
> +{
> +	struct damon_addr_range addr_range;
> +
> +	if (*start > *end)
> +		return -EINVAL;
> +
> +	if (!*start && !*end &&
> +		!damon_find_biggest_system_ram(start, end))
> +		return -EINVAL;

This function sets the region as biggest system ram only if both *start and
*end are zero.  The name should be changed, and it would better to have a
kernel doc comment as the behavior is not very simple.  How about below?

/**
 * damon_set_region_biggest_system_ram_default() - Set the region of the given
 * monitoring target as requested, or biggest 'System RAM'.
 * @t:		The monitoring target to set the region.
 * @start:	The pointer to the start address of the region.
 * @end:	The pointer to the end address of the region.
 *
 * This function sets the region of @t as requested by @start and @end.  If the
 * values of the two pointers are pointing to are zero, however, this function
 * finds the biggest 'System RAM' resource and set the region to cover the
 * resource.  In the latter case, this function saves the start and end address
 * of the resource in @start and @end, respectively.
 *
 * Return: 0 on success, negative error code otherwise.
 */

> +
> +	addr_range.start = *start;
> +	addr_range.end = *end;
> +	return damon_set_regions(t, &addr_range, 1);
> +}
> +
>  static int __init damon_init(void)
>  {
>  	damon_region_cache = KMEM_CACHE(damon_region, 0);
> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
> index d7eb72b41cb6..0276cbec632a 100644
> --- a/mm/damon/lru_sort.c
> +++ b/mm/damon/lru_sort.c
> @@ -188,7 +188,6 @@ static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
>  static int damon_lru_sort_apply_parameters(void)
>  {
>  	struct damos *scheme;
> -	struct damon_addr_range addr_range;
>  	unsigned int hot_thres, cold_thres;
>  	int err = 0;
>  
> @@ -211,15 +210,9 @@ static int damon_lru_sort_apply_parameters(void)
>  		return -ENOMEM;
>  	damon_add_scheme(ctx, scheme);
>  
> -	if (monitor_region_start > monitor_region_end)
> -		return -EINVAL;
> -	if (!monitor_region_start && !monitor_region_end &&
> -	    !damon_find_biggest_system_ram(&monitor_region_start,
> -					   &monitor_region_end))
> -		return -EINVAL;
> -	addr_range.start = monitor_region_start;
> -	addr_range.end = monitor_region_end;
> -	return damon_set_regions(target, &addr_range, 1);
> +	return damon_set_regions_from_system_ram(target,
> +				&monitor_region_start,
> +				&monitor_region_end);
>  }
>  
>  static int damon_lru_sort_turn(bool on)
> diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
> index 3d59ab11b7b3..6297e1799190 100644
> --- a/mm/damon/reclaim.c
> +++ b/mm/damon/reclaim.c
> @@ -144,7 +144,6 @@ static struct damos *damon_reclaim_new_scheme(void)
>  static int damon_reclaim_apply_parameters(void)
>  {
>  	struct damos *scheme;
> -	struct damon_addr_range addr_range;
>  	int err = 0;
>  
>  	err = damon_set_attrs(ctx, &damon_reclaim_mon_attrs);
> @@ -157,15 +156,9 @@ static int damon_reclaim_apply_parameters(void)
>  		return -ENOMEM;
>  	damon_set_schemes(ctx, &scheme, 1);
>  
> -	if (monitor_region_start > monitor_region_end)
> -		return -EINVAL;
> -	if (!monitor_region_start && !monitor_region_end &&
> -	    !damon_find_biggest_system_ram(&monitor_region_start,
> -					   &monitor_region_end))
> -		return -EINVAL;
> -	addr_range.start = monitor_region_start;
> -	addr_range.end = monitor_region_end;
> -	return damon_set_regions(target, &addr_range, 1);
> +	return damon_set_regions_from_system_ram(target,
> +				&monitor_region_start,
> +				&monitor_region_end);
>  }
>  
>  static int damon_reclaim_turn(bool on)
> -- 
> 2.27.0
> 

Thanks,
SJ