linux-kernel - Re: [PATCH] oom_kill: fix calculation of the cpu_time and the run

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Message-ID: <48EB8ACA.6030603@miraclelinux.com>
Date:	Wed, 08 Oct 2008 01:14:02 +0900
From:	Naohiro Ooiwa <nooiwa@...aclelinux.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] oom_kill: fix calculation of the cpu_time and the run_time

Hi KOSAKI-san

Thank you for quick reply and checking my patch.


> Have you seen any trouble?

No I haven't.

> in some architecture, shift-op outperfom divide-op largely.

Of course, but I think that the oom-killer doesn't need high performance.
Do you think oom-killer needs it ?

> why do you need this change?

Nothing special,
but I write a tips about oom-killer now.

The comments and the source code don't match.
so I think how to write about badness point now.

Therefore, I only think the source code should conform to the comments.


Regards,
Naohiro Ooiwa.


KOSAKI Motohiro さんは書きました:
>> Hi all
>>
>> The cpu-time is in tens of seconds
>> and the run-time is in thousands of secounds.
>>
>> but the source code doesn't follow it.
> 
> Have you seen any trouble?
> 
>> I fixed it and also some white-spaces.
>> Could you please check this patch.
>>
>>
>> Signed-off-by: Naohiro Ooiwa <nooiwa@...aclelinux.com>
>> ---
>>  mm/oom_kill.c |   10 +++++-----
>>  1 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index 64e5b4b..bddab74 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -100,14 +100,14 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
>>
>>  	/*
>>  	 * CPU time is in tens of seconds and run time is in thousands
>> -         * of seconds. There is no particular reason for this other than
>> -         * that it turned out to work very well in practice.
>> +	 * of seconds. There is no particular reason for this other than
>> +	 * that it turned out to work very well in practice.
>>  	 */
>> -	cpu_time = (cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
>> -		>> (SHIFT_HZ + 3);
>> +	cpu_time = ((cputime_to_jiffies(p->utime) + cputime_to_jiffies(p->stime))
>> +		>> SHIFT_HZ) / 10UL;
>>
>>  	if (uptime >= p->start_time.tv_sec)
>> -		run_time = (uptime - p->start_time.tv_sec) >> 10;
>> +		run_time = (uptime - p->start_time.tv_sec) / 1000UL;
>>  	else
>>  		run_time = 0;
> 
> in some architecture, shift-op outperfom divide-op largely.
> why do you need this change?
> 
> 
> 

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