Re: [PATCH] mm, oom: normalize the adj to ensure oom_badness return one

[David Rientjes]

On Mon, 3 Mar 2014, He, Bo wrote:

> if oom_score_adj is a big negative number, such as -941,
> adj *= totalpages / 1000 will be a big negative number, 
> finally the oom_badness will get 0 points, here normalize 
> the oom_score_adj to ensure oom_badness return the
> positive number.
> 

Sorry, I have no clue what you're talking about or trying to fix.

A /proc/pid/oom_score_adj of -941 would mean discounting 94.1% of system 
memory from pid's resident memory usage for a system oom condition.  This 
is the effect of adj *= totalpages / 1000 and is working as intended per 
Documentation/filesystems/proc.txt.

oom_badness() will then return the smallest integer possible, 1 (not 0), 
that still allows the process to be killed, that's the effect of 
"return points > 0 ? points : 1".  It never returns 0 as you state, you're 
either not reading the code correctly or not working on any recent kernel.

> Change-Id: I1c56a948ce48b65a1bb63b56ffef07d5d76d7ec8
> Signed-off-by: he, bo <bo.he@xxxxxxxxx>
> Signed-off-by: wang, biao <biao.wang@xxxxxxxxx>
> Reviewed-by: Yanmin Zhang <yanmin_zhang@xxxxxxxxx>
> ---
>  mm/oom_kill.c |    3 +++ 
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 3291e82..5a93986 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -181,6 +181,9 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
>         points -= (points * 3) / 100;
>  
>     /* Normalize to oom_score_adj units */
> +   if(OOM_SCORE_ADJ_MIN < 0)
> +       adj -= OOM_SCORE_ADJ_MIN;
> +
>     adj *= totalpages / 1000;
>     points += adj;
>  
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