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Subject: Re: [PATCH v2 0/3] EM / PM: Inefficient OPPs
From:   Lukasz Luba <lukasz.luba@arm.com>
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Vincent Donnefort <vincent.donnefort@arm.com>,
        peterz@infradead.org, rjw@rjwysocki.net,
        vincent.guittot@linaro.org, qperret@google.com,
        linux-kernel@vger.kernel.org, ionela.voinescu@arm.com,
        dietmar.eggemann@arm.com
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Date:   Wed, 26 May 2021 12:50:45 +0100
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On 5/26/21 11:39 AM, Lukasz Luba wrote:
> 

[snip]

To summarize:
- we don't want to disable some OPPs
- we want to give a 'hint' from energy perspective
- we rely on SchedUtil 2nd stage which clamps this
freq hint value to allowed OPPs which might set
actually not the one what we see as 'efficient'
-- we don't harm some existing platform which might
    needs these 'inefficient' OPPs in some use cases
- we pay some extra cost in this SchedUtil freq
switch path, which shouldn't harm too much.
-- we pay this cost only for arm/arm64 platforms
    which use EM
-- this cost is balanced by the benefit that we see in
    benchmarks and measured energy
-- the LUT might limit the impact

I hope this would help to better understand the scope and
impact of this patch set.

Regards,
Lukasz