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

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Date:   Mon, 18 Sep 2023 11:11:07 +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] mm/damon/core: remove unnecessary si_meminfo invoke.

Hi Huan,

On Mon, 18 Sep 2023 17:49:34 +0800 Huan Yang <link@...o.com> wrote:

> si_meminfo() will read and assign more info not just free/ram pages.

Nice catch :)

> For just DAMOS_WMARK_FREE_MEM_RATE use, only get free and ram pages
> is ok to save cpu.
> 
> Signed-off-by: Huan Yang <link@...o.com>
> ---
>  mm/damon/core.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index bcd2bd9d6c10..1cddee9ae73b 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -1278,14 +1278,16 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
>  	return true;
>  }
>  
> -static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
> +static unsigned long __damons_get_wmark_free_mem_rate(void)

Nit.  s/damons/damos/ would look more consistently, in my opinion?

>  {
> -	struct sysinfo i;
> +	return global_zone_page_state(NR_FREE_PAGES) * 1000 / totalram_pages();
> +}
>  
> +static unsigned long damos_wmark_metric_value(enum damos_wmark_metric metric)
> +{
>  	switch (metric) {
>  	case DAMOS_WMARK_FREE_MEM_RATE:
> -		si_meminfo(&i);
> -		return i.freeram * 1000 / i.totalram;
> +		return __damons_get_wmark_free_mem_rate();

Since __damons_get_wmark_free_mem_rate() is just one line function and
damos_wmark_metric_value() is the only user of the code, I think we could just
writ the code here?

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


Thanks,
SJ