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Date:   Tue, 14 Jun 2022 12:47:03 +0100
From:   Vincent Donnefort <vdonnefort@google.com>
To:     Lukasz Luba <lukasz.luba@arm.com>
Cc:     linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com,
        morten.rasmussen@arm.com, chris.redpath@arm.com,
        qperret@google.com, tao.zhou@linux.dev, kernel-team@android.com,
        peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org
Subject: Re: [PATCH v10 0/7] feec() energy margin removal
Message-ID: <Yqh1N1lhw+hukHD9@google.com>
References: <20220607123254.565579-1-vdonnefort@google.com>
 <6099583c-c986-e1f3-1eee-33b504286757@arm.com>
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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@arm.com>
> 
> to the whole patch set.
> 
> Regards,
> Lukasz

Thanks a lot Lukasz!