linux-kernel - Re: [PATCH] cpuidle: Add a predict callback for the governors

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Message-ID: <CAJZ5v0iCkMA=LVvV+-jqr8fCYz2mwaqtiKmNTfxf0dxZ=MvdiQ@mail.gmail.com>
Date:   Thu, 21 Feb 2019 17:18:25 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuidle: Add a predict callback for the governors

On Thu, Feb 21, 2019 at 3:56 PM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> Predicting the next event on the current CPU is implemented in the
> idle state selection function, thus the selection logic and the
> prediction are tied together and it is hard to decorrelate both.
>
> The following change introduces the cpuidle function to give the
> opportunity to the governor to store the guess estimate of the
> different source of wakeup and then reuse them in the selection
> process. Consequently we end up with two separate operations clearly
> identified.
>
> As the next events are stored in the cpuidle device structure it is
> easy to propagate them in the different governor callbacks.

Can you explain a bit how you would use this new callback in a governor?