linux-kernel - Re: [PATCH] sched: deduplicate mm checks in normalize_rt

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Message-ID: <BANLkTik6uerEZfULDQe9kY8L6U7OpP3Q5Q@mail.gmail.com>
Date:	Thu, 21 Apr 2011 21:50:35 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Yong Zhang <yong.zhang0@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] sched: deduplicate mm checks in normalize_rt_tasks()

On Thu, Apr 21, 2011 at 9:43 PM, Yong Zhang <yong.zhang0@...il.com> wrote:
> On Thu, Apr 21, 2011 at 09:29:04PM +0800, Yong Zhang wrote:
>> On Thu, Apr 21, 2011 at 09:15:56PM +0800, Hillf Danton wrote:
>> > When normalizing realtime tasks, only user tasks are concerned by
>> > checking their ->mm.
>> > If the task is not realtime, the -mm is checked again, thus the
>> > overwork could be removed.
>> >
>> > Signed-off-by: Hillf Danton <dhillf@...il.com>
>> > ---
>> >
>> > --- a/kernel/sched.c        2011-03-30 03:09:48.000000000 +0800
>> > +++ b/kernel/sched.c        2011-04-21 20:59:28.000000000 +0800
>> > @@ -8364,7 +8364,7 @@ void normalize_rt_tasks(void)
>> >                      * Renice negative nice level userspace
>> >                      * tasks back to 0:
>> >                      */
>> > -                   if (TASK_NICE(p) < 0 && p->mm)
>> > +                   if (TASK_NICE(p) < 0)
>>
>> This looks good.
>>
>> And we can also move TASK_NICE(p) < 0 to the upper if(),
>> like:
>>               if (!rt_task(p) && TASK_NICE(p) < 0) {
>>                       set_user_nice(p, 0);
>>                       continue;
>>               }
>>
>> to reduce one level if() to make code cleaner :)
>
> Damm, I'm wrong here, just ignore it.
>
Hi Yong

We could not be fine every time, right?

thanks
          Hillf

> Yours is good.
>
> Reviewed-by: Yong Zhang <yong.zhang0@...il.com>
>
>>
>> Thanks,
>> Yong
>>
>> >                             set_user_nice(p, 0);
>> >                     continue;
>> >             }
>> > --
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