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Date: Wed, 25 Mar 2015 16:50:40 -0700
From: Sai Gurrappadi <sgurrappadi@nvidia.com>
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To: Morten Rasmussen <morten.rasmussen@arm.com>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "mingo@redhat.com" <mingo@redhat.com>
CC: "vincent.guittot@linaro.org" <vincent.guittot@linaro.org>,
        Dietmar Eggemann <Dietmar.Eggemann@arm.com>,
        "yuyang.du@intel.com" <yuyang.du@intel.com>,
        "preeti@linux.vnet.ibm.com" <preeti@linux.vnet.ibm.com>,
        "mturquette@linaro.org" <mturquette@linaro.org>,
        "nico@linaro.org" <nico@linaro.org>,
        "rjw@rjwysocki.net" <rjw@rjwysocki.net>,
        Juri Lelli <Juri.Lelli@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Peter Boonstoppel <pboonstoppel@nvidia.com>
Subject: Re: [RFCv3 PATCH 43/48] sched: Introduce energy awareness into detach_tasks
References: <1423074685-6336-1-git-send-email-morten.rasmussen@arm.com> <1423074685-6336-44-git-send-email-morten.rasmussen@arm.com>
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On 02/04/2015 10:31 AM, Morten Rasmussen wrote:
> From: Dietmar Eggemann <dietmar.eggemann@arm.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