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

[Michal Hocko <mhocko@suse.com>]

On Sat 29-08-26 20:13:10, Andrew Morton wrote:
> On Tue, 11 Aug 2026 11:36:08 +0800 Ye Liu <ye.liu@linux.dev> wrote:
> 
> > From: Ye Liu <liuye@kylinos.cn>
> > 
> > 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.
> > 
> > ...
> >
> > --- 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;
> 
> AI review suggests that this is a misinterpretation of "1000"?
> 
> 	https://sashiko.dev/#/patchset/20260811033609.3992348-1-ye.liu@linux.dev

Sashiko is trying to be clever and it is simply wrong here. The scaling
fact is indeed the same as the OOM_SCORE_ADJ_MAX.

-- 
Michal Hocko
SUSE Labs