linux-kernel - Re: [PATCH v12 4/4] PM / Domains: Add genpd governor for CPUs

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Message-ID: <89b2583d-672c-4264-a627-d0b606c3d076@linaro.org>
Date:   Thu, 21 Mar 2019 12:41:39 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>, linux-pm@...r.kernel.org
Cc:     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>,
        "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-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 4/4] PM / Domains: Add genpd governor for CPUs

On 27/02/2019 20:58, Ulf Hansson wrote:
> As it's now perfectly possible that a PM domain managed by genpd contains
> devices belonging to CPUs, we should start to take into account the
> residency values for the idle states during the state selection process.
> The residency value specifies the minimum duration of time, the CPU or a
> group of CPUs, needs to spend in an idle state to not waste energy entering
> it.
> 
> To deal with this, let's add a new genpd governor, pm_domain_cpu_gov, that
> may be used for a PM domain that have CPU devices attached or if the CPUs
> are attached through subdomains.
> 
> The new governor computes the minimum expected idle duration time for the
> online CPUs being attached to the PM domain and its subdomains. Then in the
> state selection process, trying the deepest state first, it verifies that
> the idle duration time satisfies the state's residency value.
> 
> It should be noted that, when computing the minimum expected idle duration
> time, we use the information about the next timer/tick that is stored in
> the per CPU variable, cpuidle_devices, for the related CPUs. Future wise,
> this deserves to be improved, as there are obviously more reasons to why a
> CPU may be woken up from idle.
> 
> Cc: Lina Iyer <ilina@...eaurora.org>
> Co-developed-by: Lina Iyer <lina.iyer@...aro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>



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