linux-kernel - Re: [PATCH] sched/isolation: delete redundant housekeeping

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Message-ID: <20211124092103.64e93376@gmail.com>
Date:   Wed, 24 Nov 2021 09:21:03 +0800
From:   Aili Yao <yaoaili126@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        bsegall@...gle.com, mgorman@...e.de, linux-kernel@...r.kernel.org,
        yaoaili@...gsoft.com
Subject: Re: [PATCH] sched/isolation: delete redundant
 housekeeping_overridden check

On Tue, 23 Nov 2021 12:38:52 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 23 Nov 2021 15:45:35 +0800
> Aili Yao <yaoaili126@...il.com> wrote:
> 
> > From: Aili Yao <yaoaili@...gsoft.com>
> > 
> > housekeeping_test_cpu is only called by housekeeping_cpu(),
> > and in housekeeping_cpu(), there is already one same check;
> > 
> > So delete the redundant check.
> > 
> > Signed-off-by: Aili Yao <yaoaili@...gsoft.com>
> > ---
> >  kernel/sched/isolation.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> > index 7f06eaf..5c4d533 100644
> > --- a/kernel/sched/isolation.c
> > +++ b/kernel/sched/isolation.c
> > @@ -56,9 +56,8 @@ void housekeeping_affine(struct task_struct *t, enum
> > hk_flags flags) 
> >  bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
> >  {
> > -	if (static_branch_unlikely(&housekeeping_overridden))
> > -		if (housekeeping_flags & flags)
> > -			return cpumask_test_cpu(cpu,
> > housekeeping_mask);  
> 
> Not only is your email client broken, you don't seem to understand what
> static_branch_unlikely() is.

Yes, My mail client is not properly configured, sorry for that, I will make it work.

And Yes again, I have limited knowledge about static key, But still don't understand why we
need two same check(jump or nop instruction?) here, could you be kindly to explain this?

A lot Thanks!
Aili Yao