linux-kernel - Re: [RFCv3 PATCH 33/48] sched: Energy-aware wake-up task placement

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Message-ID: <20150324130058.GN23123@twins.programming.kicks-ass.net>
Date:	Tue, 24 Mar 2015 14:00:58 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	mingo@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, yuyang.du@...el.com,
	preeti@...ux.vnet.ibm.com, mturquette@...aro.org, nico@...aro.org,
	rjw@...ysocki.net, juri.lelli@....com, linux-kernel@...r.kernel.org
Subject: Re: [RFCv3 PATCH 33/48] sched: Energy-aware wake-up task placement

On Wed, Feb 04, 2015 at 06:31:10PM +0000, Morten Rasmussen wrote:
> @@ -5138,6 +5224,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
>  		prev_cpu = cpu;
>  
>  	if (sd_flag & SD_BALANCE_WAKE) {
> +		if (energy_aware()) {
> +			new_cpu = energy_aware_wake_cpu(p);
> +			goto unlock;
> +		}
>  		new_cpu = select_idle_sibling(p, prev_cpu);
>  		goto unlock;
>  	}

So that is fundamentally wrong I think. We only care about power aware
scheduling when U < 1, after that we should do the normal thing. This
setup does not allow for that.
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