linux-kernel - Re: [PATCH] cfs: remove unused 'if' condition checking

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Date:	Fri, 16 Sep 2011 16:17:00 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Paul Turner <pjt@...gle.com>
Cc:	Wang Xingchao <xingchao.wang@...el.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org
Subject: Re: [PATCH] cfs: remove unused 'if' condition checking

On Fri, Sep 16, 2011 at 12:41:07AM -0700, Paul Turner wrote:
> On 09/16/11 10:35, Wang Xingchao wrote:
> 
> Please include a one-line summary such as:
> sched: remove extra nr_running check in check_preempt_tick
> 
> > nr_running must be more than 1, so remove the checking
> >
> 
> Sure, reasonable.
> 
> Please expand this comment though, e.g.
> We already test for nr_running > 1 within entity_tick so there is no
> need to recheck it within check_preempt_tick().
> 
> > Signed-off-by: Wang Xingchao<xingchao.wang@...el.com>
> 
> Reviewed-by: Paul Turner <pjt@...gle.com>
> 
> > ---
> >   kernel/sched_fair.c |   16 ++++++++--------
> >   1 files changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
> > index 1ca2cd4..fef0bfd 100644
> > --- a/kernel/sched_fair.c
> > +++ b/kernel/sched_fair.c
> > @@ -1106,6 +1106,8 @@ static void
> >   check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
> >   {
> >       unsigned long ideal_runtime, delta_exec;
> > +    struct sched_entity *se;
> > +    s64 delta;
> >
> >       ideal_runtime = sched_slice(cfs_rq, curr);
> >       delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
> > @@ -1127,16 +1129,14 @@ check_preempt_tick(struct cfs_rq *cfs_rq,
> struct sched_entity *curr)
> >       if (delta_exec<  sysctl_sched_min_granularity)
> 
> You've mangled the white space on the less-than.

But it looks ok on my side.
And on LKML: https://lkml.org/lkml/2011/9/16/11

So maybe it's not Xingchao's problem.

Thanks,
Yong

> 
> >           return;
> >
> > -    if (cfs_rq->nr_running>  1) {
> > -        struct sched_entity *se = __pick_first_entity(cfs_rq);
> > -        s64 delta = curr->vruntime - se->vruntime;
> > +    se = __pick_first_entity(cfs_rq);
> > +    delta = curr->vruntime - se->vruntime;
> >
> > -        if (delta<  0)
> > -            return;
> > +    if (delta<  0)
> 
> And here.
> 
> > +        return;
> >
> > -        if (delta>  ideal_runtime)
> > -            resched_task(rq_of(cfs_rq)->curr);
> > -    }
> > +    if (delta>  ideal_runtime)
> 
> Here too.
> 
> > +        resched_task(rq_of(cfs_rq)->curr);
> >   }
> >
> >   static void
> 
> --
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