linux-kernel - Re: [RFC PATCH v3 04/10] PM / EM: Expose the Energy Model in sysfs

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Message-ID: <20180619121643.GR2458@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Jun 2018 14:16:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     rjw@...ysocki.net, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        mingo@...hat.com, dietmar.eggemann@....com,
        morten.rasmussen@....com, chris.redpath@....com,
        patrick.bellasi@....com, valentin.schneider@....com,
        vincent.guittot@...aro.org, thara.gopinath@...aro.org,
        viresh.kumar@...aro.org, tkjos@...gle.com, joelaf@...gle.com,
        smuckle@...gle.com, adharmap@...cinc.com, skannan@...cinc.com,
        pkondeti@...eaurora.org, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [RFC PATCH v3 04/10] PM / EM: Expose the Energy Model in sysfs

On Mon, May 21, 2018 at 03:24:59PM +0100, Quentin Perret wrote:
> This exposes the Energy Model (read-only) of all frequency domains in
> sysfs for convenience. To do so, a parent kobject is added to the CPU
> subsystem under the umbrella of which a kobject for each frequency
> domain is attached.
> 
> The resulting hierarchy is as follows for a platform with two frequency
> domains for example:
> 
>    /sys/devices/system/cpu/energy_model
>    ├── fd0
>    │   ├── capacity
>    │   ├── cpus
>    │   ├── frequency
>    │   └── power
>    └── fd4
>        ├── capacity
>        ├── cpus
>        ├── frequency
>        └── power
> 

Given that each FD can have multiple {freq,power} tuples and sysfs has a
one value per file policy, how does this work?