linux-kernel - Re: [PATCH V1 1/2] mm/damon/sysfs: avoid call damon_target_has

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Message-Id: <20220916084251.105360-1-sj@kernel.org>
Date:   Fri, 16 Sep 2022 08:42:51 +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 V1 1/2] mm/damon/sysfs: avoid call damon_target_has_pid() repeatedly

On Thu, 15 Sep 2022 22:22:36 +0800 Xin Hao <xhao@...ux.alibaba.com> wrote:

> In damon_sysfs_destroy_targets(), we call damon_target_has_pid() to
> check whether the 'ctx' include a valid pid, but there no need to call
> damon_target_has_pid() to check repeatedly, just need call it once.

Good eyes, nice finding!

> 
> Signed-off-by: Xin Hao <xhao@...ux.alibaba.com>
> ---
>  mm/damon/sysfs.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
> index 1fa0023f136e..966ea7892ccf 100644
> --- a/mm/damon/sysfs.c
> +++ b/mm/damon/sysfs.c
> @@ -2143,9 +2143,13 @@ static int damon_sysfs_set_attrs(struct damon_ctx *ctx,
>  static void damon_sysfs_destroy_targets(struct damon_ctx *ctx)
>  {
>  	struct damon_target *t, *next;
> +	bool has_pid = false;
> +
> +	if (damon_target_has_pid(ctx))
> +		has_pid = true;

How about doing more simple and short like below?

    bool has_pid = damon_target_has_pid(ctx)

Other than this,

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


Thanks,
SJ

> 
>  	damon_for_each_target_safe(t, next, ctx) {
> -		if (damon_target_has_pid(ctx))
> +		if (has_pid)
>  			put_pid(t->pid);
>  		damon_destroy_target(t);
>  	}
> --
> 2.31.0