linux-kernel - Re: [PATCH V3] mm/damon: simplify scheme create in lru

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Date:   Thu, 15 Sep 2022 13:25:06 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Xin Hao <xhao@...ux.alibaba.com>
Cc:     sj@...nel.org, akpm@...ux-foundation.org, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] mm/damon: simplify scheme create in lru_sort.c

Hi Xin,

On Thu, 15 Sep 2022 10:36:55 +0800 Xin Hao <xhao@...ux.alibaba.com> wrote:

> In damon_lru_sort_new_hot_scheme() and damon_lru_sort_new_cold_scheme(),
> they have so much in common, so we can combine them into a single
> function, and we just need to distinguish their differences.
> 
> Suggested-by: SeongJae Park <sj@...nel.org>
> Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
> Changes from v2
> (https://lore.kernel.org/linux-mm/20220914113859.37637-1-xhao@linux.alibaba.com/)
> - Add static global 'struct damos_access_pattern' stub variable

Chagelog should not be in the commit message area,

> ---

but here.

>  mm/damon/lru_sort.c | 41 +++++++++++++++++++----------------------
>  1 file changed, 19 insertions(+), 22 deletions(-)
> 
> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
> index 07a0908963fd..6a26c5822286 100644
> --- a/mm/damon/lru_sort.c
> +++ b/mm/damon/lru_sort.c
> @@ -132,6 +132,18 @@ DEFINE_DAMON_MODULES_DAMOS_STATS_PARAMS(damon_lru_sort_cold_stat,
>  		lru_sort_tried_cold_regions, lru_sorted_cold_regions,
>  		cold_quota_exceeds);
> 
> +struct damos_access_pattern damon_lru_sort_stub_access_pattern = {
> +	/* Find regions having PAGE_SIZE or larger size */
> +	.min_sz_region = PAGE_SIZE,
> +	.max_sz_region = ULONG_MAX,
> +	/* and accessed for more than the threshold */

This comment looks inappropriate.  How about 'no matter its access frequency'?

> +	.min_nr_accesses = 0,
> +	.max_nr_accesses = UINT_MAX,
> +	/* no matter its age */
> +	.min_age_region = 0,
> +	.max_age_region = UINT_MAX,
> +};
> +
>  static struct damon_ctx *ctx;
>  static struct damon_target *target;
> 
> @@ -157,17 +169,9 @@ static struct damos *damon_lru_sort_new_scheme(
>  /* Create a DAMON-based operation scheme for hot memory regions */
>  static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
>  {
> -	struct damos_access_pattern pattern = {
> -		/* Find regions having PAGE_SIZE or larger size */
> -		.min_sz_region = PAGE_SIZE,
> -		.max_sz_region = ULONG_MAX,
> -		/* and accessed for more than the threshold */
> -		.min_nr_accesses = hot_thres,
> -		.max_nr_accesses = UINT_MAX,
> -		/* no matter its age */
> -		.min_age_region = 0,
> -		.max_age_region = UINT_MAX,
> -	};
> +	struct damos_access_pattern pattern = damon_lru_sort_stub_access_pattern;

More than 80 columns.  Renaming stub_access_pattern into stub_pattern might
make sense.

> +
> +	pattern.min_nr_accesses = hot_thres;
> 
>  	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_PRIO);
>  }
> @@ -175,17 +179,10 @@ static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
>  /* Create a DAMON-based operation scheme for cold memory regions */
>  static struct damos *damon_lru_sort_new_cold_scheme(unsigned int cold_thres)
>  {
> -	struct damos_access_pattern pattern = {
> -		/* Find regions having PAGE_SIZE or larger size */
> -		.min_sz_region = PAGE_SIZE,
> -		.max_sz_region = ULONG_MAX,
> -		/* and not accessed at all */
> -		.min_nr_accesses = 0,
> -		.max_nr_accesses = 0,
> -		/* for min_age or more micro-seconds */
> -		.min_age_region = cold_thres,
> -		.max_age_region = UINT_MAX,
> -	};
> +	struct damos_access_pattern pattern = damon_lru_sort_stub_access_pattern;

More than 80 columns.

> +
> +	pattern.max_nr_accesses = 0;
> +	pattern.min_age_region = cold_thres;
> 
>  	return damon_lru_sort_new_scheme(&pattern, DAMOS_LRU_DEPRIO);
>  }
> --
> 2.31.0

Other than the trivial things, look good.  As my comments are only for trivial
cosmetic things, I will make the change and post v4 on my own.


Thanks,
SJ