linux-kernel - Re: [PATCH v3 2/5] sched: Take cpufreq feedback into account

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Date: Tue, 9 Jan 2024 12:22:01 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Vincent Guittot <vincent.guittot@...aro.org>, linux@...linux.org.uk,
 catalin.marinas@....com, will@...nel.org, sudeep.holla@....com,
 rafael@...nel.org, viresh.kumar@...aro.org, agross@...nel.org,
 andersson@...nel.org, konrad.dybcio@...aro.org, mingo@...hat.com,
 peterz@...radead.org, juri.lelli@...hat.com, rostedt@...dmis.org,
 bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
 vschneid@...hat.com, lukasz.luba@....com, rui.zhang@...el.com,
 mhiramat@...nel.org, daniel.lezcano@...aro.org, amit.kachhap@...il.com,
 corbet@....net, gregkh@...uxfoundation.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Cc: qyousef@...alina.io
Subject: Re: [PATCH v3 2/5] sched: Take cpufreq feedback into account

On 08/01/2024 14:48, Vincent Guittot wrote:
> Aggregate the different pressures applied on the capacity of CPUs and
> create a new function that returns the actual capacity of the CPU:
>   get_actual_cpu_capacity()

   function name                scaling

(1) arch_scale_cpu_capacity() -	uarch

(2) get_actual_cpu_capacity() -	hw + cpufreq/thermal of (1)

(3) capacity_of()	      -	rt (rt/dl/irq) of (2) (used by fair)

Although (1) - (3) are very close to each other from the functional
standpoint, their names are not very coherent.

I assume this makes it hard to understand all of this when reading the
code w/o knowing these patches before.

Why is (2) tagged with 'actual'?

This is especially visible in feec() where local variable cpu_cap
relates to (3) whereas cpu_actual_cap related to (2).

[...]