linux-kernel - Re: [RFC PATCH v3 05/10] sched/topology: Reference the Energy Model of CPUs when available

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Message-ID: <20180619122632.GS2458@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Jun 2018 14:26:32 +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 05/10] sched/topology: Reference the Energy Model
 of CPUs when available

On Mon, May 21, 2018 at 03:25:00PM +0100, Quentin Perret wrote:
> In order to use EAS, the task scheduler has to know about the Energy
> Model (EM) of the platform. This commit extends the scheduler topology
> code to take references on the frequency domains objects of the EM
> framework for all online CPUs. Hence, the availability of the EM for
> those CPUs is guaranteed to the scheduler at runtime without further
> checks in latency sensitive code paths (i.e. task wake-up).

I'm confused by this patch,... what does it do? Why is em_cpu_get()
(after you fix it) not sufficient?