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

[Ye Liu <ye.liu@linux.dev>]

在 2026/8/18 09:04, Song Hu 写道:
> On 2026/8/11 11:36, Ye Liu wrote:
>> --- 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;
> 
> One thing this line hides: for a memcg OOM, totalpages is
> mem_cgroup_get_max(), which can be below 1000 pages when the
> container limit is under 4M.  The division then yields 0, the whole
> oom_score_adj contribution goes away, and a task protected with
> -997 scores the same as a best-effort task with 1000.  The -1000
> exemption is checked separately above and still works.
> 
> DIV_ROUND_UP(totalpages, OOM_SCORE_ADJ_MAX) would preserve the adj
> weighting for small limits and change nothing meaningful for large
> ones.  This is an edge case, so probably fine to leave as is -
> noting it here since the line is being touched anyway.

Good catch. Yes, the truncation for totalpages < 1000 is real, 
but as you noted, it's an existing edge case. I'll keep this patch 
as a mechanical replacement and won't address it here. Out of curiosity,
are sub-4MB memcg limits actually used in practice? 

-- 
Thanks,
Ye Liu