linux-kernel - Re: [PATCH 8/8] sched,fair: flatten hierarchical runqueues

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Date:   Tue, 25 Jun 2019 11:50:23 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Rik van Riel <riel@...riel.com>, peterz@...radead.org
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org, kernel-team@...com,
        morten.rasmussen@....com, tglx@...utronix.de,
        dietmar.eggeman@....com, mgorman@...hsingularity.com,
        vincent.guittot@...aro.org
Subject: Re: [PATCH 8/8] sched,fair: flatten hierarchical runqueues

On 6/12/19 9:32 PM, Rik van Riel wrote:

[...]

> @@ -410,6 +412,11 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
>  	return se->parent;
>  }
>  
> +static inline bool task_se_in_cgroup(struct sched_entity *se)
> +{
> +	return parent_entity(se);
> +}

IMHO, s/in_cgroup/not_in_root_tg/ reads easier. "/", i.e. the root tg is
still a cgroup, I guess. But you could use existing parent_entity(se) as
well.

[...]

> @@ -679,22 +710,16 @@ static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
>  static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  {
>  	u64 slice = sysctl_sched_latency;
> +	struct load_weight *load = &cfs_rq->load;
> +	struct load_weight lw;
>  
> -	for_each_sched_entity(se) {
> -		struct load_weight *load;
> -		struct load_weight lw;
> +	if (unlikely(!se->on_rq)) {
> +		lw = cfs_rq->load;
>  
> -		cfs_rq = cfs_rq_of(se);
> -		load = &cfs_rq->load;
> -
> -		if (unlikely(!se->on_rq)) {
> -			lw = cfs_rq->load;
> -
> -			update_load_add(&lw, se->load.weight);
> -			load = &lw;
> -		}
> -		slice = __calc_delta(slice, se->load.weight, load);
> +		update_load_add(&lw, task_se_h_load(se));
> +		load = &lw;
>  	}
> +	slice = __calc_delta(slice, task_se_h_load(se), load);

task_se_h_load(se) and se->load.weight are off my factor of >= 1024 on
64bit.

...
    bash pid=3250: task_se_h_load(se)=1023 se->load.weight=1048576
    sysctl_sched_latency=18000000 slice=0 old_slice=17999995
...

[...]