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

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Date:	Thu, 21 Apr 2011 21:43:12 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Hillf Danton <dhillf@...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 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.

Yours is good.

Reviewed-by: Yong Zhang <yong.zhang0@...il.com>

> 
> Thanks,
> Yong
> 
> >  				set_user_nice(p, 0);
> >  			continue;
> >  		}
> > --
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