linux-kernel - Re: [RFCv3 PATCH 43/48] sched: Introduce energy awareness into detach

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Message-ID: <551349D0.8070402@nvidia.com>
Date:	Wed, 25 Mar 2015 16:50:40 -0700
From:	Sai Gurrappadi <sgurrappadi@...dia.com>
To:	Morten Rasmussen <morten.rasmussen@....com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>
CC:	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	"yuyang.du@...el.com" <yuyang.du@...el.com>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"mturquette@...aro.org" <mturquette@...aro.org>,
	"nico@...aro.org" <nico@...aro.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <Juri.Lelli@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Boonstoppel <pboonstoppel@...dia.com>
Subject: Re: [RFCv3 PATCH 43/48] sched: Introduce energy awareness into detach_tasks

On 02/04/2015 10:31 AM, Morten Rasmussen wrote:
> From: Dietmar Eggemann <dietmar.eggemann@....com>
>  	while (!list_empty(tasks)) {
> @@ -6121,6 +6121,20 @@ static int detach_tasks(struct lb_env *env)
>  		if (!can_migrate_task(p, env))
>  			goto next;
>  
> +		if (env->use_ea) {
> +			struct energy_env eenv = {
> +				.src_cpu = env->src_cpu,
> +				.dst_cpu = env->dst_cpu,
> +				.usage_delta = task_utilization(p),
> +			};
> +			int e_diff = energy_diff(&eenv);
> +
> +			if (e_diff >= 0)
> +				goto next;
> +
> +			goto detach;
> +		}
> +
>  		load = task_h_load(p);
>  
>  		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
> @@ -6129,6 +6143,7 @@ static int detach_tasks(struct lb_env *env)
>  		if ((load / 2) > env->imbalance)
>  			goto next;
>  
> +detach:
>  		detach_task(p, env);
>  		list_add(&p->se.group_node, &env->tasks);

Hi Morten, Dietmar,

Wouldn't the above energy_diff() use the 'old' value of dst_cpu's util?
Tasks are detached/dequeued in this loop so they have their util
contrib. removed from src_cpu but their contrib. hasn't been added to
dst_cpu yet (happens in attach_tasks).

Thanks,
-Sai
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