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

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Message-ID: <4E72FD93.2060805@google.com>
Date:	Fri, 16 Sep 2011 00:41:07 -0700
From:	Paul Turner <pjt@...gle.com>
To:	Wang Xingchao <xingchao.wang@...el.com>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu, peterz@...radead.org,
	yong.zhang0@...il.com
Subject: Re: [PATCH] cfs: remove unused 'if' condition checking

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.

 >           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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