Re: [PATCH v3]mm/oom-kill: direct hardware access processes should get bonus

[KOSAKI Motohiro]

> the victim should not directly access hardware devices like Xorg server,
> because the hardware could be left in an unpredictable state, although 
> user-application can set /proc/pid/oom_score_adj to protect it. so i think
> those processes should get bonus for protection.
> 
> in v2, fix the incorrect comment.
> in v3, change the divided the badness score by 4, like old heuristic for protection. we just
> want the oom_killer don't select Root/RESOURCE/RAWIO process as possible.
> 
> suppose that if a user process A such as email cleint "evolution" and a process B with
> ditecly hareware access such as "Xorg", they have eat the equal memory (the badness score is 
> the same),so which process are you want to kill? so in new heuristic, it will kill the process B.
> but in reality, we want to kill process A.
> 
> Signed-off-by: Figo.zhang <figo1802@xxxxxxxxx>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>

Sorry for the delay. I've sent completely revert patch to linus. It will
disappear your headache, I believe. I'm sorry that our development
caused your harm. We really don't want it.

Thanks.


> ---
> mm/oom_kill.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 4029583..f43d759 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -202,6 +202,15 @@ unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
>  		points -= 30;
>  
>  	/*
> +	 * Root and direct hareware access processes are usually more 
> +	 * important, so they should get bonus for protection. 
> +	 */
> +	if (has_capability_noaudit(p, CAP_SYS_ADMIN) ||
> +	    has_capability_noaudit(p, CAP_SYS_RESOURCE) ||
> +	    has_capability_noaudit(p, CAP_SYS_RAWIO))
> +		points /= 4;
> +
> +	/*
>  	 * /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
>  	 * either completely disable oom killing or always prefer a certain
>  	 * task.
> 
> 



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