linux-kernel - Re: [RESEND][PATCH 0/8] Introduce support for artificial Energy Model

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Message-ID: <55d4a19d-15d4-4d15-8430-8a8ed8149497@arm.com>
Date:   Tue, 12 Apr 2022 07:53:19 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     rafael@...nel.org
Cc:     dietmar.eggemann@....com, Pierre.Gondois@....com,
        ionela.voinescu@....com, viresh.kumar@...aro.org,
        daniel.lezcano@...aro.org, linux-pm@...r.kernel.org,
        mka@...omium.org, nm@...com, sboyd@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, cristian.marussi@....com,
        sudeep.holla@....com, matthias.bgg@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND][PATCH 0/8] Introduce support for artificial Energy Model

Hi Rafael,

gentle ping. If you need some help with this maintenance,
we can help.

Regards,
Lukasz

On 4/4/22 13:35, Lukasz Luba wrote:
> Hi Rafael,
> 
> 
> The patch set has been on LKML for quite a while and got one ACK,
> for the code touching something outside the EM (thermal cooling).
> 
> AFAICS there is no interest and objections from others for this code.
> 
> Therefore, I have a question:
> What would be be process to have merge this code?
> (We had internally a few reviews of this code)
> 
> On 3/21/22 09:57, Lukasz Luba wrote:
>> Hi all,
>>
>> This patch set adds new callback and support for artificial Energy 
>> Model (EM).
>> The new EMs have artificially generated performance states.
>> Such EMs can be created from lean information sources, such
>> as the relative energy efficiency between CPUs. The ACPI based
>> platforms provide this information
>> (ACPI 6.4, s5.2.12.14 'GIC CPU Interface (GICC) Structure'
>> 'Processor Power efficiency Class' field).
>>
>> Artificial EMs might require to directly provide the 'cost' of
>> the generated performance state. This patch set adds a new callback
>> .get_cost() for this. The EM framework does not force any model
>> or formula, it's up to the platform code.
>>
>> Artificial EMs aim to leverage the Energy Aware Scheduler
>> (EAS). Other frameworks relying on performance states
>> information (i.e. IPA/DTPM) must be informed of the
>> EM type and might be prevented from using it. This patch
>> sets also does this by introducing a new flag:
>> EM_PERF_DOMAIN_ARTIFICIAL.
>>
>> The patch set is based on current linux-next, where some
>> changes to OPP & EM are queuing.
>>
>> The patch set also contains (patch 7/8 and patch 8/8) logic which 
>> prevents
>> two EM's client frameworks from using this new EM type. Some other 
>> approach,
>> using 'milli-watts', has been proposed and discussed, but refused [1].
>> This new flag is more precised and should not leave space for
>> wrong interpretation.
>>
>> Shortly after this patch set you will see a patch set implementing the
>> platform code and registering this new EM.
>>
> 
> 
> No one from Arm is an official maintainer of the EM code.
> 
> Regards,
> Lukasz