linux-kernel - Re: [PATCH] sched/cpufreq: Align trace event behavior of fast switching

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Message-ID: <eccb89bf-80cc-e96a-925e-181095305631@arm.com>
Date:   Mon, 26 Aug 2019 14:12:56 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Douglas RAILLARD <douglas.raillard@....com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        viresh.kumar@...aro.org, mingo@...hat.com
Subject: Re: [PATCH] sched/cpufreq: Align trace event behavior of fast
 switching

On 26/08/2019 13:24, Peter Zijlstra wrote:
> On Mon, Aug 26, 2019 at 11:51:17AM +0200, Dietmar Eggemann wrote:
> 
>> Not sure about the extra  'if trace_cpu_frequency_enabled()' but I guess
>> it doesn't hurt.
> 
> Without that you do that for_each_cpu() iteration unconditionally, even
> if the tracepoint is disabled.

Makes sense, I'm wondering if we want this in
cpufreq_notify_transition() CPUFREQ_POSTCHANGE for the
non-fast-switching drivers as well.