linux-kernel - Re: [PATCH 3/5] oom: oom-killer don't use proportion of system-ram internally

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Message-ID: <BANLkTinb3Yuvrz5b-dyGYv0_HMB9+ax3yA@mail.gmail.com>
Date:	Tue, 24 May 2011 10:32:43 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, caiqian@...hat.com, rientjes@...gle.com,
	hughd@...gle.com, kamezawa.hiroyu@...fujitsu.com, oleg@...hat.com
Subject: Re: [PATCH 3/5] oom: oom-killer don't use proportion of system-ram internally

On Tue, May 24, 2011 at 10:14 AM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
> Hi
>
>
>>> @@ -476,14 +476,17 @@ static const struct file_operations
>>> proc_lstats_operations = {
>>>
>>>  static int proc_oom_score(struct task_struct *task, char *buffer)
>>>  {
>>> -       unsigned long points = 0;
>>> +       unsigned long points;
>>> +       unsigned long ratio = 0;
>>> +       unsigned long totalpages = totalram_pages + total_swap_pages + 1;
>>
>> Does we need +1?
>> oom_badness does have the check.
>
> "ratio = points * 1000 / totalpages;" need to avoid zero divide.
>
>>>        /*
>>>         * Root processes get 3% bonus, just like the __vm_enough_memory()
>>>         * implementation used by LSMs.
>>> +        *
>>> +        * XXX: Too large bonus, example, if the system have tera-bytes
>>> memory..
>>>         */
>>> -       if (has_capability_noaudit(p, CAP_SYS_ADMIN))
>>> -               points -= 30;
>>> +       if (has_capability_noaudit(p, CAP_SYS_ADMIN)) {
>>> +               if (points>= totalpages / 32)
>>> +                       points -= totalpages / 32;
>>> +               else
>>> +                       points = 0;
>>
>> Odd. Why do we initialize points with 0?
>>
>> I think the idea is good.
>
> The points is unsigned. It's common technique to avoid underflow.
>

Thanks for explanation, KOSAKI.
I need sleeping. :(



-- 
Kind regards,
Minchan Kim
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