linux-kernel - Re: [RFC PATCH V2 1/3] sched/fair: Fixup-wake_up_sync-vs-DELAYED

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Message-ID: <CAB8ipk94m_aD8-Pd2hTrkqhDJkq-scnO3zq4wsY4LSnnL-YD0A@mail.gmail.com>
Date: Tue, 20 May 2025 14:00:35 +0800
From: Xuewen Yan <xuewen.yan94@...il.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Xuewen Yan <xuewen.yan@...soc.com>, peterz@...radead.org, mingo@...hat.com, 
	juri.lelli@...hat.com, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	linux-kernel@...r.kernel.org, ke.wang@...soc.com, di.shen@...soc.com
Subject: Re: [RFC PATCH V2 1/3] sched/fair: Fixup-wake_up_sync-vs-DELAYED_DEQUEUE

Hi Vincent,

Sorry to ask, but may I know if this patch can be merged into the mainline?

Thanks!

On Wed, Mar 19, 2025 at 5:35 PM Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> On Mon, 3 Mar 2025 at 11:56, Xuewen Yan <xuewen.yan@...soc.com> wrote:
> >
> > Delayed dequeued feature keeps a sleeping task enqueued until its
> > lag has elapsed. As a result, it stays also visible in rq->nr_running.
> > So when in wake_affine_idle(), we should use the real running-tasks
> > in rq to check whether we should place the wake-up task to
> > current cpu.
> > On the other hand, add a helper function to return the nr-delayed.
> >
> > Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
> > Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
>
> Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
>
> > ---
> > V2:
> > - add helper function (Vincent)
> > ---
> >  kernel/sched/fair.c | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 1c0ef435a7aa..a354f29c4f6f 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -7181,6 +7181,11 @@ static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> >         return true;
> >  }
> >
> > +static inline unsigned int cfs_h_nr_delayed(struct rq *rq)
> > +{
> > +       return (rq->cfs.h_nr_queued - rq->cfs.h_nr_runnable);
> > +}
> > +
> >  #ifdef CONFIG_SMP
> >
> >  /* Working cpumask for: sched_balance_rq(), sched_balance_newidle(). */
> > @@ -7342,8 +7347,12 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
> >         if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
> >                 return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
> >
> > -       if (sync && cpu_rq(this_cpu)->nr_running == 1)
> > -               return this_cpu;
> > +       if (sync) {
> > +               struct rq *rq = cpu_rq(this_cpu);
> > +
> > +               if ((rq->nr_running - cfs_h_nr_delayed(rq)) == 1)
> > +                       return this_cpu;
> > +       }
> >
> >         if (available_idle_cpu(prev_cpu))
> >                 return prev_cpu;
> > --
> > 2.25.1
> >