linux-kernel - Re: [PATCH v14 4/4] PM / Domains: Add genpd governor for CPUs

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Date:   Thu, 11 Apr 2019 22:44:29 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Raju P . L . S . S . S . N" <rplsssn@...eaurora.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v14 4/4] PM / Domains: Add genpd governor for CPUs

On Thu, Apr 11, 2019 at 8:17 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> After some preceding changes, PM domains managed by genpd may contain
> CPU devices, so idle state residency values should be taken into
> account during the state selection process. [The residency value is
> the minimum amount of time to be spent by a CPU (or a group of CPUs)
> in an idle state in order to save more energy than could be saved
> by picking up a shallower idle state.]
>
> For this purpose, add a new genpd governor, pm_domain_cpu_gov, to be
> used for selecting idle states of PM domains with CPU devices attached
> either directly or through subdomains.
>
> The new governor computes the minimum expected idle duration for all
> online CPUs attached to a PM domain and its subdomains.  Next, it
> finds the deepest idle state whose target residency is within the
> expected idle duration and selects it as the target idle state of
> the domain.
>
> It should be noted that the minimum expected idle duration computation
> is based on the closest timer event information stored in the per-CPU
> variables cpuidle_devices for all of the CPUs in the domain.  That
> needs to be revisited in future, as obviously there are other reasons
> why a CPU may be woken up from idle.
>
> Co-developed-by: Lina Iyer <lina.iyer@...aro.org>
> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> [ rjw: Changelog ]
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Applied instead of the previous version, thanks!