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

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Message-ID: <20180619184250.GF2494@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Jun 2018 20:42:50 +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 Tue, Jun 19, 2018 at 06:13:17PM +0100, Quentin Perret wrote:
> I agree having one list per root_domain should be better. I'll change that
> in v4. But I also think the idea of a global static_key is broken then.

Static keys are global per definition, there is only a single copy of
the code.

You have to enable if there is a root domain with more than 1
freq-domain.

> We need a per root_domain thing as well. The SD_ASYM_CPUCAPACITY flag
> might be set on one hierarchy and not the other for ex. Not sure if
> attaching a static_key to each root_domain really makes sense though ...
> 
> Would replacing the static_key by a flag attached to the root_domain be
> reasonable ? 

Keep the static key as is, enable if any root domain needs it.

> > (and an empty list if there is but one entry on).
> 
> Sorry but I didn't understand that ...

If you have only a single freq-domain, there is nothing to do, right?