linux-kernel - Re: [PATCH 13/23] sched,ion: Convert to sched_set

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Message-ID: <20200422132923.GK20730@hirez.programming.kicks-ass.net>
Date:   Wed, 22 Apr 2020 15:29:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Qais Yousef <qais.yousef@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH 13/23] sched,ion: Convert to sched_set_normal()

On Wed, Apr 22, 2020 at 03:21:45PM +0200, Vincent Guittot wrote:
> On Wed, 22 Apr 2020 at 13:29, Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > In an attempt to take away sched_setscheduler() from modules, change
> > this into sched_set_normal(.nice = 19).
> >
> > Cc: john.stultz@...aro.org
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Reviewed-by: Ingo Molnar <mingo@...nel.org>
> > ---
> >  drivers/staging/android/ion/ion_heap.c |    3 ---
> >  1 file changed, 3 deletions(-)
> >
> > --- a/drivers/staging/android/ion/ion_heap.c
> > +++ b/drivers/staging/android/ion/ion_heap.c
> > @@ -244,8 +244,6 @@ static int ion_heap_deferred_free(void *
> >
> >  int ion_heap_init_deferred_free(struct ion_heap *heap)
> >  {
> > -       struct sched_param param = { .sched_priority = 0 };
> > -
> >         INIT_LIST_HEAD(&heap->free_list);
> >         init_waitqueue_head(&heap->waitqueue);
> >         heap->task = kthread_run(ion_heap_deferred_free, heap,
> > @@ -255,7 +253,7 @@ int ion_heap_init_deferred_free(struct i
> >                        __func__);
> >                 return PTR_ERR_OR_ZERO(heap->task);
> >         }
> > -       sched_setscheduler(heap->task, SCHED_IDLE, &param);
> > +       sched_set_normal(heap->task, 19);
> 
> Would it make sense to have a sched_set_idle(task) to enable kernel
> setting SCHED_IDLE task ?
> 
> SCHED_NORMAL w/ nice 19 and SCHED_IDLE tasks are not treated in the
> same way when checking for preemption at  wakeup

Yeah, but does it really matter? I did indeed consider it, but got
lazy. Is there a definite need for IDLE?