linux-kernel - Re: [PATCH 09/10] sched,fair: add helper functions for flattened runqueue

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Date:   Mon, 1 Jul 2019 16:20:31 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Rik van Riel <riel@...riel.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, pjt@...gle.com,
        dietmar.eggemann@....com, peterz@...radead.org, mingo@...hat.com,
        morten.rasmussen@....com, tglx@...utronix.de,
        mgorman@...hsingularity.net, vincent.guittot@...aro.org
Subject: Re: [PATCH 09/10] sched,fair: add helper functions for flattened
 runqueue

On Fri, Jun 28, 2019 at 04:49:12PM -0400, Rik van Riel wrote:
> Add helper functions to make the flattened runqueue patch a little smaller.
> 
> The task_se_h_weight function is similar to task_se_h_load, but scales the
> task weight by the group weight, without taking the task's duty cycle into
> account.
> 
> The task_se_in_cgroup helper is functionally identical to parent_entity,
> but directly calling a function with that name obscures what the other
> code is trying to use it for, and would make the code harder to understand.
> 
> Signed-off-by: Rik van Riel <riel@...riel.com>
> ---
>  kernel/sched/fair.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a751e7a9b228..6fea8849cc12 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -243,6 +243,7 @@ static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight
>  
>  const struct sched_class fair_sched_class;
>  static unsigned long task_se_h_load(struct sched_entity *se);
> +static unsigned long task_se_h_weight(struct sched_entity *se);
>  
>  /**************************************************************
>   * CFS operations on generic schedulable entities:
> @@ -411,6 +412,12 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
>  	return se->parent;
>  }
>  
> +/* Is this (task) sched_entity in a non-root cgroup? */
> +static inline bool task_se_in_cgroup(struct sched_entity *se)
> +{
> +	return parent_entity(se);
> +}
> +
>  static void
>  find_matching_se(struct sched_entity **se, struct sched_entity **pse)
>  {
> @@ -7819,6 +7826,20 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
>  	}
>  }
>  
> +static unsigned long task_se_h_weight(struct sched_entity *se)
> +{
> +	struct cfs_rq *cfs_rq;
> +
> +	if (!task_se_in_cgroup(se))
> +		return se->load.weight;
> +
> +	cfs_rq = group_cfs_rq_of_parent(se);
> +	update_cfs_rq_h_load(cfs_rq);
> +
> +	/* Reduce the load.weight by the h_load of the group the task is in. */
> +	return (cfs_rq->h_load * se->load.weight) >> SCHED_FIXEDPOINT_SHIFT;

This should be

scale_load_down(cfs_rq->h_load * se->load.weight);

Thanks,

Josef