Re: [PATCH] mm/oom_kill, proc: replace magic number 1000 with OOM_SCORE_ADJ_MAX

On Tue 11-08-26 11:36:08, Ye Liu wrote:
> From: Ye Liu <[email protected]>
> 
> In oom_badness() and proc_oom_score(), the oom_score_adj normalization
> uses a hardcoded 1000, which is the value of OOM_SCORE_ADJ_MAX defined
> in include/uapi/linux/oom.h.  Other code in the kernel (e.g.
> fs/proc/base.c oom_adj handling) already uses OOM_SCORE_ADJ_MAX for
> the same purpose.
> 
> Replace the magic number with the macro for consistency and
> readability.  No functional change.
> 
> Signed-off-by: Ye Liu <[email protected]>

I am not really sure this adds to the readability much TBH but no
fundamental objections from me.

Acked-by: Michal Hocko <[email protected]>

> ---
>  fs/proc/base.c | 3 ++-
>  mm/oom_kill.c  | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 6a39de424f62..58be38942460 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -594,7 +594,8 @@ static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
>  	 * exporting for a long time so userspace might depend on it.
>  	 */
>  	if (badness != LONG_MIN)
> -		points = (1000 + badness * 1000 / (long)totalpages) * 2 / 3;
> +		points = (OOM_SCORE_ADJ_MAX +
> +			  badness * OOM_SCORE_ADJ_MAX / (long)totalpages) * 2 / 3;
>  
>  	seq_printf(m, "%lu\n", points);
>  
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 5f372f6e26fa..08bff7a55db8 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -230,7 +230,7 @@ long oom_badness(struct task_struct *p, unsigned long totalpages)
>  	task_unlock(p);
>  
>  	/* Normalize to oom_score_adj units */
> -	adj *= totalpages / 1000;
> +	adj *= totalpages / OOM_SCORE_ADJ_MAX;
>  	points += adj;
>  
>  	return points;
> -- 
> 2.25.1

-- 
Michal Hocko
SUSE Labs