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

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Message-ID: <6099583c-c986-e1f3-1eee-33b504286757@arm.com>
Date:   Thu, 9 Jun 2022 13:53:22 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Vincent Donnefort <vdonnefort@...gle.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

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