linux-kernel - Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks

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Message-ID: <CAKfTPtA87ST1uiVaABHDocxG=s8VGa0mmE8jdmVECZSoNJvEqw@mail.gmail.com>
Date:	Tue, 21 Jun 2016 14:36:46 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Yuyang Du <yuyang.du@...el.com>, Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Benjamin Segall <bsegall@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks

On 21 June 2016 at 13:43, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Jun 20, 2016 at 11:23:39AM +0200, Vincent Guittot wrote:
>
>> Don't we have to do a complete attach with attach_task_cfs_rq instead
>> of just the load_avg ? to set also depth ?
>
> Hmm, yes, your sched_set_group() change seems to have munged this.
>

I think that it was done by the attach_task_cfs_rq during the activate_task.
Now, the attach is done in post_init_entity_util_avg. Can't we just
set the depth in post_init_entity_util_avg ?

> Previously we'd call task_move_group_fair() which would indeed setup
> depth.
>
> I've changed it thus (all smaller edits just didn't look right):
>
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7743,7 +7743,7 @@ void sched_offline_group(struct task_gro
>   * group pointers. The task will be attached to the runqueue during its wake
>   * up.
>   */
> -static void sched_set_group(struct task_struct *tsk, bool move)
> +static void sched_change_group(struct task_struct *tsk, int type)
>  {
>         struct task_group *tg;
>
> @@ -7758,8 +7758,8 @@ static void sched_set_group(struct task_
>         tsk->sched_task_group = tg;
>
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> -       if (move && tsk->sched_class->task_move_group)
> -               tsk->sched_class->task_move_group(tsk);
> +       if (tsk->sched_class->task_change_group)
> +               tsk->sched_class->task_change_group(tsk, type);
>         else
>  #endif
>                 set_task_rq(tsk, task_cpu(tsk));
> @@ -7788,7 +7788,7 @@ void sched_move_task(struct task_struct
>         if (unlikely(running))
>                 put_prev_task(rq, tsk);
>
> -       sched_set_group(tsk, true);
> +       sched_change_group(tsk, TASK_MOVE_GROUP);
>
>         if (unlikely(running))
>                 tsk->sched_class->set_curr_task(rq);
> @@ -8227,7 +8227,7 @@ static void cpu_cgroup_fork(struct task_
>
>         rq = task_rq_lock(task, &rf);
>
> -       sched_set_group(task, false);
> +       sched_change_group(task, TASK_SET_GROUP);
>
>         task_rq_unlock(rq, task, &rf);
>  }
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8443,6 +8443,14 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
>  }
>
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> +static void task_set_group_fair(struct task_struct *p)
> +{
> +       struct sched_entity *se = &p->se;
> +
> +       set_task_rq(p, task_cpu(p));
> +       se->depth = se->parent ? se->parent->depth + 1 : 0;
> +}
> +
>  static void task_move_group_fair(struct task_struct *p)
>  {
>         detach_task_cfs_rq(p);
> @@ -8455,6 +8463,19 @@ static void task_move_group_fair(struct
>         attach_task_cfs_rq(p);
>  }
>
> +static void task_change_group_fair(struct task_struct *p, int type)
> +{
> +       switch (type) {
> +       case TASK_SET_GROUP:
> +               task_set_group_fair(p);
> +               break;
> +
> +       case TASK_MOVE_GROUP:
> +               task_move_group_fair(p);
> +               break;
> +       }
> +}
> +
>  void free_fair_sched_group(struct task_group *tg)
>  {
>         int i;
> @@ -8683,7 +8704,7 @@ const struct sched_class fair_sched_clas
>         .update_curr            = update_curr_fair,
>
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> -       .task_move_group        = task_move_group_fair,
> +       .task_change_group      = task_change_group_fair,
>  #endif
>  };
>
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1247,7 +1247,10 @@ struct sched_class {
>         void (*update_curr) (struct rq *rq);
>
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> -       void (*task_move_group) (struct task_struct *p);
> +#define TASK_SET_GROUP  0
> +#define TASK_MOVE_GROUP        1
> +
> +       void (*task_change_group) (struct task_struct *p, int type);
>  #endif
>  };
>