linux-kernel - Re: [PATCH v10 0/7] feec() energy margin removal

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Date:   Tue, 14 Jun 2022 12:47:03 +0100
From:   Vincent Donnefort <vdonnefort@...gle.com>
To:     Lukasz Luba <lukasz.luba@....com>
Cc:     linux-kernel@...r.kernel.org, dietmar.eggemann@....com,
        morten.rasmussen@....com, chris.redpath@....com,
        qperret@...gle.com, tao.zhou@...ux.dev, kernel-team@...roid.com,
        peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org
Subject: Re: [PATCH v10 0/7] feec() energy margin removal

On Thu, Jun 09, 2022 at 01:53:22PM +0100, Lukasz Luba wrote:
> Hi Vincent,
> 
> On 6/7/22 13:32, Vincent Donnefort wrote:
> > Hi,
> > 
> > Here's a new version of the patch-set to get rid of the energy margin in
> > feec(). Many thanks to all for the insightful comments I got.
> > 
> > find_energy_efficient() (feec()) will migrate a task to save energy only if
> > it saves at least 6% of the total energy consumed by the system. This
> > conservative approach is a problem on a system where a lot of small tasks
> > create a huge load on the overall: very few of them will be allowed to
> > migrate to a smaller CPU, wasting a lot of energy. Instead of trying to
> > determine yet another margin, let's try to remove it.
> > 
> > The first elements of this patch-set are various fixes and improvement that
> > stabilizes task_util and ensures energy comparison fairness across all CPUs
> > of the topology. Only once those fixed, we can completely remove the margin
> > and let feec() aggressively place task and save energy.
> > 
> 
> I've run this patch set on pixel6 (android-mainline) and gathered energy
> values from the meter during the PCmark 3.0.
> 
> It looks good, with these patches we have ~10% lower energy usage and
> only ~3% lower score.
> 
> There are no other issues, everything works fine. Feel free to add:
> 
> Tested-by: Lukasz Luba <lukasz.luba@....com>
> 
> to the whole patch set.
> 
> Regards,
> Lukasz

Thanks a lot Lukasz!