linux-kernel - Re: [PATCH 3/5] intel_pstate: remove intel

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Message-ID: <CAJvTdKmmHSM8FJq=1d4vQAYg=orgHb7OFRLmZ7EH2yWM7mQcAg@mail.gmail.com>
Date:   Fri, 16 Jun 2017 21:10:39 -0400
From:   Len Brown <lenb@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     X86 ML <x86@...nel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get()

>> >> -             get_avg_frequency(cpu),
>> >> +             aperfmperf_khz_on_cpu(cpu->cpu),
>>
>> Note that I deleted the line above in an updated version of this patch
>> that I'm ready to send out.
>>
>> There were a couple of problems with it.
>> The first is that it was  ugly that tracing (which occurs only in the
>> SW governor case)
>> could shorten the measurement interval as seen by the sysfs interface.
>>
>> The second is that this trace point can be called with irqs off,
>> and smp_call_function_single() will WARN when called with irqs off.
>>
>> Srinivas Acked that I simply remove this field from the tracepoint --
>> as it is redundant to calculate it in the kernel when we are already
>> exporting the raw values of aperf and mperf.
>
> This changes the tracepoint format and I know about a couple of user space
> scripts that consume these tracepoints though.
> What would be wrong with leaving it as is?

I'm fine keeping get_avg_frequency() for the purpose of just this tracepoint
compatibility, if you think it is useful to do so.

I removed it because its only function was the (removed) intel_pstate.get()
and this tracepoint.  And this tracepoint already includes aperf and mperf,
which can be used to calculate frequency in user-space, if desired.
Srinivas Acked' that updating his user-space script would be fine --
dunno if that is sufficient.

cheers,
-Len