linux-kernel - Re: [PATCH v2] mm/damon/core: remove unnecessary si

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Date:   Tue, 19 Sep 2023 15:38:28 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Huan Yang <link@...o.com>
Cc:     SeongJae Park <sj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        damon@...ts.linux.dev (open list:DATA ACCESS MONITOR),
        linux-mm@...ck.org (open list:DATA ACCESS MONITOR),
        linux-kernel@...r.kernel.org (open list),
        opensource.kernel@...o.com
Subject: Re: [PATCH v2] mm/damon/core: remove unnecessary si_meminfo invoke.

Hi Huan,

On Tue, 19 Sep 2023 10:00:57 +0800 Huan Yang <link@...o.com> wrote:

> si_meminfo() will read and assign more info not just free/ram pages.
> For just DAMOS_WMARK_FREE_MEM_RATE use, only get free and ram pages
> is ok to save cpu.
> 
> Change from v1:
> v1 fold free mem rate logic into __damos_get_wmark_free_mem_rate and not
> invoke si_meminfo, just get free/ram_pages in global.
> v2 cancel this __damos_get_wmark_free_mem_rate and just calculate rate
> in damos_wmark_metric_value to keep it simple.

Thank you for accepting my suggestion and making this change.  Nevertheless, we
usually not keep patch changelogs on commit message but after the '---'
line[1].

> 
> Signed-off-by: Huan Yang <link@...o.com>

Other than above and below trivial comments,

Reviewed-by: SeongJae Park <sj@...nel.org>

> ---

This is usual place for patch changelogs.


>  mm/damon/core.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index bcd2bd9d6c10..a3f812d78267 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1280,12 +1280,9 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
>  
>  static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
>  {
> -	struct sysinfo i;
> -
>  	switch (metric) {
>  	case DAMOS_WMARK_FREE_MEM_RATE:
> -		si_meminfo(&i);
> -		return i.freeram * 1000 / i.totalram;
> +		return global_zone_page_state(NR_FREE_PAGES) * 1000 / totalram_pages();

DAMON code still prefer 80 columns limit[2] (sorry for being stubborn).  Could
you please break this line for that?

>  	default:
>  		break;
>  	}
> -- 
> 2.34.1
> 

[1] https://docs.kernel.org/process/submitting-patches.html#the-canonical-patch-format
[2] https://docs.kernel.org/process/coding-style.html#indentation

Thanks,
SJ