linux-kernel - Re: [PATCH] sched/fair: Remove the force parameter of update_tg_load

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Message-ID: <CAKfTPtBx7F_TMSMy2OKDPZNyHwJfVvsDbNo45sM_kAHQTK8zEw@mail.gmail.com>
Date:   Fri, 25 Sep 2020 16:11:53 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Xianting Tian <tian.xianting@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: Remove the force parameter of update_tg_load_avg()

On Thu, 24 Sep 2020 at 03:55, Xianting Tian <tian.xianting@....com> wrote:
>
> In the file fair.c, sometims update_tg_load_avg(cfs_rq, 0) is used,
> sometimes update_tg_load_avg(cfs_rq, false) is used.
> update_tg_load_avg() has the parameter force, but in current code,
> it never set 1 or true to it, so remove the force parameter.
>
> Signed-off-by: Xianting Tian <tian.xianting@....com>

Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>

> ---
>  kernel/sched/fair.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1a68a0536..7056fa97f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -831,7 +831,7 @@ void init_entity_runnable_average(struct sched_entity *se)
>  void post_init_entity_util_avg(struct task_struct *p)
>  {
>  }
> -static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
> +static void update_tg_load_avg(struct cfs_rq *cfs_rq)
>  {
>  }
>  #endif /* CONFIG_SMP */
> @@ -3288,7 +3288,6 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
>  /**
>   * update_tg_load_avg - update the tg's load avg
>   * @cfs_rq: the cfs_rq whose avg changed
> - * @force: update regardless of how small the difference
>   *
>   * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
>   * However, because tg->load_avg is a global value there are performance
> @@ -3300,7 +3299,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
>   *
>   * Updating tg's load_avg is necessary before update_cfs_share().
>   */
> -static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
> +static inline void update_tg_load_avg(struct cfs_rq *cfs_rq)
>  {
>         long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
>
> @@ -3310,7 +3309,7 @@ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
>         if (cfs_rq->tg == &root_task_group)
>                 return;
>
> -       if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
> +       if (abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
>                 atomic_long_add(delta, &cfs_rq->tg->load_avg);
>                 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
>         }
> @@ -3612,7 +3611,7 @@ static inline bool skip_blocked_update(struct sched_entity *se)
>
>  #else /* CONFIG_FAIR_GROUP_SCHED */
>
> -static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
> +static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) {}
>
>  static inline int propagate_entity_load_avg(struct sched_entity *se)
>  {
> @@ -3800,13 +3799,13 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>                  * IOW we're enqueueing a task on a new CPU.
>                  */
>                 attach_entity_load_avg(cfs_rq, se);
> -               update_tg_load_avg(cfs_rq, 0);
> +               update_tg_load_avg(cfs_rq);
>
>         } else if (decayed) {
>                 cfs_rq_util_change(cfs_rq, 0);
>
>                 if (flags & UPDATE_TG)
> -                       update_tg_load_avg(cfs_rq, 0);
> +                       update_tg_load_avg(cfs_rq);
>         }
>  }
>
> @@ -7887,7 +7886,7 @@ static bool __update_blocked_fair(struct rq *rq, bool *done)
>                 struct sched_entity *se;
>
>                 if (update_cfs_rq_load_avg(cfs_rq_clock_pelt(cfs_rq), cfs_rq)) {
> -                       update_tg_load_avg(cfs_rq, 0);
> +                       update_tg_load_avg(cfs_rq);
>
>                         if (cfs_rq == &rq->cfs)
>                                 decayed = true;
> @@ -10786,7 +10785,7 @@ static void detach_entity_cfs_rq(struct sched_entity *se)
>         /* Catch up with the cfs_rq and remove our load when we leave */
>         update_load_avg(cfs_rq, se, 0);
>         detach_entity_load_avg(cfs_rq, se);
> -       update_tg_load_avg(cfs_rq, false);
> +       update_tg_load_avg(cfs_rq);
>         propagate_entity_cfs_rq(se);
>  }
>
> @@ -10805,7 +10804,7 @@ static void attach_entity_cfs_rq(struct sched_entity *se)
>         /* Synchronize entity with its cfs_rq */
>         update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
>         attach_entity_load_avg(cfs_rq, se);
> -       update_tg_load_avg(cfs_rq, false);
> +       update_tg_load_avg(cfs_rq);
>         propagate_entity_cfs_rq(se);
>  }
>
> --
> 2.17.1
>