linux-kernel - Re: [PATCH v10 2/7] sched: Rewrite runnable load and utilization average tracking

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Date:	Fri, 24 Jul 2015 17:41:35 +0100
From:	Dietmar Eggemann <dietmar.eggemann@....com>
To:	Yuyang Du <yuyang.du@...el.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	"pjt@...gle.com" <pjt@...gle.com>,
	"bsegall@...gle.com" <bsegall@...gle.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"umgwanakikbuti@...il.com" <umgwanakikbuti@...il.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"fengguang.wu@...el.com" <fengguang.wu@...el.com>
Subject: Re: [PATCH v10 2/7] sched: Rewrite runnable load and utilization
 average tracking

Hi Yuyang,

On 15/07/15 01:04, Yuyang Du wrote:

[...]

> @@ -4674,7 +4487,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
>                 /*
>                  * w = rw_i + @wl
>                  */
> -               w = se->my_q->load.weight + wl;
> +               w = se->my_q->avg.load_avg + wl;
> 
>                 /*
>                  * wl = S * s'_i; see (2)

There is a comment 'Per the above, wl is the new *se->load.weight*
value'. This should be replaced by *se->avg.load_avg*. Also the function
header explains the functionality of effective_load() based on weight
and not sched_avg::load_avg.

> @@ -4695,7 +4508,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
>                 /*
>                  * wl = dw_i = S * (s'_i - s_i); see (3)
>                  */
> -               wl -= se->load.weight;
> +               wl -= se->avg.load_avg;
> 
>                 /*
>                  * Recursively apply this logic to all parent groups to compute
> @@ -4769,14 +4582,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>          */
>         if (sync) {
>                 tg = task_group(current);
> -               weight = current->se.load.weight;
> +               weight = current->se.avg.load_avg;
> 
>                 this_load += effective_load(tg, this_cpu, -weight, -weight);
>                 load += effective_load(tg, prev_cpu, 0, -weight);
>         }
> 
>         tg = task_group(p);
> -       weight = p->se.load.weight;
> +       weight = p->se.avg.load_avg;

You changed cfs_rq->load.weight to cfs_rq->avg.load_avg and
se->load.weight to se->avg.load_avg in effective_load() and
wake_affine() in v2.
I wasn't able to find explanation why you did this. I mean we still have
to maintain 'struct load_weight' on cfs_rq's and se's representing tg's.

-- Dietmar

[...]

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