linux-kernel - Re: [PATCH 1/7 v4] sched: factorize attach entity

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Date:   Wed, 12 Oct 2016 12:59:52 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Wanpeng Li <kernellwp@...il.com>,
        Yuyang Du <yuyang.du@...el.com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Paul Turner <pjt@...gle.com>,
        Benjamin Segall <bsegall@...gle.com>
Subject: Re: [PATCH 1/7 v4] sched: factorize attach entity

On 7 October 2016 at 01:11, Vincent Guittot <vincent.guittot@...aro.org> wrote:
>
> On 5 October 2016 at 11:38, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> > On 09/26/2016 01:19 PM, Vincent Guittot wrote:
> >>
> >> Factorize post_init_entity_util_avg and part of attach_task_cfs_rq
> >> in one function attach_entity_cfs_rq
> >>
> >> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> >> ---
> >>  kernel/sched/fair.c | 19 +++++++++++--------
> >>  1 file changed, 11 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> >> index 986c10c..e8ed8d1 100644
> >> --- a/kernel/sched/fair.c
> >> +++ b/kernel/sched/fair.c
> >> @@ -697,9 +697,7 @@ void init_entity_runnable_average(struct sched_entity
> >> *se)
> >>  }
> >>
> >>  static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
> >> -static int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool
> >> update_freq);
> >> -static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force);
> >> -static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct
> >> sched_entity *se);
> >> +static void attach_entity_cfs_rq(struct sched_entity *se);
> >>
> >>  /*
> >>   * With new tasks being created, their initial util_avgs are extrapolated
> >> @@ -764,9 +762,7 @@ void post_init_entity_util_avg(struct sched_entity
> >> *se)
> >>               }
> >>       }
> >
> >
> > You now could move the 'u64 now = cfs_rq_clock_task(cfs_rq);' into the
> > if condition to handle !fair_sched_class tasks.
>
> yes
>
> >
> >> -     update_cfs_rq_load_avg(now, cfs_rq, false);
> >> -     attach_entity_load_avg(cfs_rq, se);
> >> -     update_tg_load_avg(cfs_rq, false);
> >> +     attach_entity_cfs_rq(se);
> >>  }
> >>
> >>  #else /* !CONFIG_SMP */
> >> @@ -8501,9 +8497,8 @@ static void detach_task_cfs_rq(struct task_struct
> >> *p)
> >>       update_tg_load_avg(cfs_rq, false);
> >>  }
> >>
> >> -static void attach_task_cfs_rq(struct task_struct *p)
> >> +static void attach_entity_cfs_rq(struct sched_entity *se)
> >>  {
> >> -     struct sched_entity *se = &p->se;
> >>       struct cfs_rq *cfs_rq = cfs_rq_of(se);
> >
> >
> > Both callers of attach_entity_cfs_rq() already use cfs_rq_of(se). You
> > could pass it into attach_entity_cfs_rq().
>
> Yes that would make sense

In fact there is a 3rd caller online_fair_sched_group which calls
attach_entity_cfs_rq and doesn't already use  cfs_rq_of(se) so i
wonder if it's worth doing the interface change.


>
>
> >
> >>       u64 now = cfs_rq_clock_task(cfs_rq);
> >> @@ -8519,6 +8514,14 @@ static void attach_task_cfs_rq(struct task_struct
> >> *p)
> >
> >
> > The old comment /* Synchronize task ... */ should be changed to /*
> > Synchronize entity ... */
>
> yes
>
> >
> >>       update_cfs_rq_load_avg(now, cfs_rq, false);
> >>       attach_entity_load_avg(cfs_rq, se);
> >>       update_tg_load_avg(cfs_rq, false);
> >> +}
> >> +
> >> +static void attach_task_cfs_rq(struct task_struct *p)
> >> +{
> >> +     struct sched_entity *se = &p->se;
> >> +     struct cfs_rq *cfs_rq = cfs_rq_of(se);
> >> +
> >> +     attach_entity_cfs_rq(se);
> >>
> >>       if (!vruntime_normalized(p))
> >>               se->vruntime += cfs_rq->min_vruntime;
> >>
> >
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