linux-kernel - Re: [PATCH] cpufreq: schedutil: Always trace frequency if it does not change

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Date:   Wed, 22 Mar 2017 18:13:21 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH] cpufreq: schedutil: Always trace frequency if it does not change

On Wed, Mar 22, 2017 at 3:21 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Mar 22, 2017 at 01:52:04PM +0100, Rafael J. Wysocki wrote:
>> On Wed, Mar 22, 2017 at 10:29 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>
>> > So why not fix the tools?
>>
>> Because I can't.
>>
>> I just can't go and fix all of the tools binaries that people use out
>> there and I want them to use recent kernels at the same time.
>>
>
> Thing is; you're now letting random tracepoint user dictate kernel
> implementation. That's a bad state to be in.

Fair enough.

Admittedly, I was sort of divided on whether or not to drop the
trace_cpu_frequency() call entirely and now I see another reason to do
that.  There is a change queued up for 4.12 that will cause the
tracepoint to be triggered more often totally in vain which I don't
think is a good thing at all.  So I'll send a v2 dropping that call
and we'll see if anyone complains.