linux-kernel - Re: [PATCH] sched: move access of avg_rt and avg

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Message-ID: <ZYNGShf8SYMkhRic@gmail.com>
Date: Wed, 20 Dec 2023 20:53:46 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>, peterz@...radead.org,
	dietmar.eggemann@....com, linux-kernel@...r.kernel.org,
	srikar@...ux.vnet.ibm.com, yu.c.chen@...el.com,
	tim.c.chen@...ux.intel.com
Subject: Re: [PATCH] sched: move access of avg_rt and avg_dl into existing
 helper functions


* Vincent Guittot <vincent.guittot@...aro.org> wrote:

> On Wed, 20 Dec 2023 at 07:55, Shrikanth Hegde
> <sshegde@...ux.vnet.ibm.com> wrote:
> >
> > This is a minor code simplification. There are helper functions called
> > cpu_util_dl and cpu_util_rt which gives the average utilization of DL
> > and RT respectively. But there are few places in code where these
> > variables are used directly.
> >
> > Instead use the helper function so that code becomes simpler and easy to
> > maintain later on.
> >
> > Signed-off-by: Shrikanth Hegde <sshegde@...ux.vnet.ibm.com>
> > ---
> >  kernel/sched/fair.c | 12 +++++-------
> >  1 file changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index bcea3d55d95d..02631060ca7e 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -9212,19 +9212,17 @@ static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
> >
> >  static inline bool others_have_blocked(struct rq *rq)
> >  {
> > -       if (READ_ONCE(rq->avg_rt.util_avg))
> > +       if (cpu_util_rt(rq))
> >                 return true;
> >
> > -       if (READ_ONCE(rq->avg_dl.util_avg))
> > +       if (cpu_util_dl(rq))
> >                 return true;
> >
> >         if (thermal_load_avg(rq))
> >                 return true;
> >
> > -#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
> > -       if (READ_ONCE(rq->avg_irq.util_avg))
> > +       if (cpu_util_irq(rq))
> 
> cpu_util_irq doesn't call READ_ONCE()

Oh, that's nasty - according to the title only avg_rt and avg_dl were 
changed, which I double checked, but the patch indeed does more ...

I've removed this patch from tip:sched/core.

Thanks,

	Ingo