linux-kernel - RE: [PATCH 1/1] scheduler: minor improvement to pick_next_highest_task

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Message-ID: <2EF88150C0EF2C43A218742ED384C1BC0FC8438B@IRVEXCHMB08.corp.ad.broadcom.com>
Date:	Wed, 21 Mar 2012 07:49:49 +0000
From:	"Michael J. Wang" <mjwang@...adcom.com>
To:	"Yong Zhang" <yong.zhang0@...il.com>
cc:	"mingo@...e.hu" <mingo@...e.hu>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rostedt@...dmis.org" <rostedt@...dmis.org>,
	"Michael J. Wang" <mjwang@...adcom.com>
Subject: RE: [PATCH 1/1] scheduler: minor improvement to
 pick_next_highest_task_rt in linux-3.3


> From: Yong Zhang [mailto:yong.zhang0@...il.com]
> Sent: Tuesday, March 20, 2012 7:12 PM
> To: Michael J. Wang
> Cc: mingo@...e.hu; peterz@...radead.org; linux-kernel@...r.kernel.org;
> rostedt@...dmis.org
> Subject: Re: [PATCH 1/1] scheduler: minor improvement to
> pick_next_highest_task_rt in linux-3.3
> 
> On Wed, Mar 21, 2012 at 01:56:47AM +0000, Michael J. Wang wrote:
> > Ah, I see.  Forgot about the length of my comment line.
> >
> > Should I reformat my patch and send it again?
> 
> It'll be better, and I think Peter/Ingo will happy with it.
> 

OK.  I will resend now.  Thanks for all your help!

Michael


> Thanks,
> Yong
> 
> >
> > Thanks,
> > Michael
> >
> >
> > -----Original Message-----
> > From: Yong Zhang [mailto:yong.zhang0@...il.com]
> > Sent: Tuesday, March 20, 2012 6:41 PM
> > To: Michael J. Wang
> > Cc: mingo@...e.hu; peterz@...radead.org; linux-
> kernel@...r.kernel.org; rostedt@...dmis.org
> > Subject: Re: [PATCH 1/1] scheduler: minor improvement to
> pick_next_highest_task_rt in linux-3.3
> >
> > On Mon, Mar 19, 2012 at 10:26:19PM +0000, Michael J. Wang wrote:
> > > From: Michael J Wang <mjwang@...adcom.com>
> > >
> > > Avoid extra work by continuing on to the next rt_rq if the highest
> prio task in current rt_rq is the same priority as our candidate task.
> > >
> > > Signed-off-by: Michael J Wang <mjwang@...adcom.com>
> > >
> > > ---
> > >
> > > More detailed explanation:  if next is not NULL, then we have found
> a candidate task, and its priority is next->prio.  Now we are looking
> for an even higher priority task in the other rt_rq's.  idx is the
> highest priority in the current candidate rt_rq.  In the current 3.3
> code, if idx is equal to next->prio, we would start scanning the tasks
> in that rt_rq and replace the current candidate task with a task from
> that rt_rq.  But the new task would only have a priority that is equal
> to our previous candidate task, so we have not advanced our goal of
> finding a higher prio task.  So we should avoid the extra work by
> continuing on to the next rt_rq if idx is equal to next->prio.
> > >
> >
> > You should limit characters of each line to 80 if possible.
> >
> > And before sending you patch, linux-source/scripts/checkpatch.pl
> maybe
> > give you some clues whether there is some warning/error. If there
> are,
> > fix them.
> >
> > Only for what your patch wants to show:
> > Reviewed-by: Yong Zhang <yong.zhang0@...il.com>
> >
> > Thanks,
> > Yong
> >
> > > --- linux-3.3/kernel/sched/rt.c.orig	2012-03-18 16:15:34.000000000
> -0700
> > > +++ linux-3.3/kernel/sched/rt.c	2012-03-19 14:52:54.585391702 -0700
> > > @@ -1403,7 +1403,7 @@ static struct task_struct *pick_next_hig
> > >  next_idx:
> > >  		if (idx >= MAX_RT_PRIO)
> > >  			continue;
> > > -		if (next && next->prio < idx)
> > > +		if (next && next->prio <= idx)
> > >  			continue;
> > >  		list_for_each_entry(rt_se, array->queue + idx, run_list) {
> > >  			struct task_struct *p;
> > >
> > >
> > >
> > >
> > >
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe linux-
> kernel" in
> > > the body of a message to majordomo@...r.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > Please read the FAQ at  http://www.tux.org/lkml/
> >
> > --
> > Only stand for myself
> >
> >
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> --
> Only stand for myself