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From:   Vincent Guittot <vincent.guittot@linaro.org>
Date:   Mon, 21 Jun 2021 11:17:00 +0200
Message-ID: <CAKfTPtDjFqWBubop-Vnr4B+PXoO3Omu6kW_0LCPqxryx=QydVw@mail.gmail.com>
Subject: Re: [PATCH 1/2] sched/rt: Fix RT utilization tracking during policy change
To:     Vincent Donnefort <vincent.donnefort@arm.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Mon, 21 Jun 2021 at 11:03, Vincent Donnefort
<vincent.donnefort@arm.com> wrote:
>
> [...]
>
> > >         /*
> > > -        * If we are already running, then there's nothing
> > > -        * that needs to be done. But if we are not running
> > > -        * we may need to preempt the current running task.
> > > -        * If that current running task is also an RT task
> > > +        * If we are not running we may need to preempt the current
> > > +        * running task. If that current running task is also an RT task
> > >          * then see if we can move to another run queue.
> > >          */
> > >         if (task_on_rq_queued(p) && rq->curr != p) {
> > > @@ -2355,6 +2353,13 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p)
> > >                 if (p->prio < rq->curr->prio && cpu_online(cpu_of(rq)))
> > >                         resched_curr(rq);
> > >         }
> > > +
> > > +       /*
> > > +        * If we are running, update the avg_rt tracking, as the running time
> > > +        * will now on be accounted into the latter.
> > > +        */
> > > +       if (task_current(rq, p))
> >
> > task_current(rq,p) equals the "rq->curr != p" above. Having 2
> > different ways to get the same value in the function is a bit
> > confusing.
> >
> > And call it once
> >
> > Otherwise, the fix looks good to me
>
> I can change it to something like:
>
> if (task_current(rq, p)) {
>     update_rt_rq_load_avg()
>     return;
> }
>
> if (task_on_rq_queued(p) {
>         ...
>         if (p->prio ...)
>                 resched_curr(rq);
> }
>
> ?

yes, looks good to me


>
> >
> > > +               update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
> > >  }
> > >
> > >  /*
> > > --
> > > 2.7.4
> > >