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Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get()

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On Sat, Jun 17, 2017 at 3:21 AM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Friday, June 16, 2017 09:10:39 PM Len Brown wrote:
>> >> >> -             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.
>
> Well, we can try to make this change and see if there are any complaints
> about it.
>
> But the Srinivas' script is in the tree, so it would be good to update it too
> along with the tracepoint.

On a second thought, in order to compute the frequency, user space
needs to know the scaling and the max_pstate_physical value too, which
may not be straightforward to obtain (on some Atoms, for example).

So why don't we leave the tracepoint as is for now?

Thanks,
Rafael

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[PATCH 0/5] x86, cpufreq: consolidate APERF/MPERF calculation Len Brown <lenb@kernel.org> - 2017-06-08 04:40 +0200
  [PATCH 2/5] x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF Len Brown <lenb@kernel.org> - 2017-06-08 04:40 +0200
    Re: [PATCH 2/5] x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:40 +0200
      Re: [PATCH 2/5] x86: use common aperfmperf_khz_on_cpu() to calculate  KHz using APERF/MPERF Len Brown <lenb@kernel.org> - 2017-06-17 03:50 +0200
        Re: [PATCH 2/5] x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-19 14:40 +0200
          Re: [PATCH 2/5] x86: use common aperfmperf_khz_on_cpu() to calculate KHz using APERF/MPERF "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-19 16:30 +0200
  [PATCH 3/5] intel_pstate: remove intel_pstate.get() Len Brown <lenb@kernel.org> - 2017-06-08 04:40 +0200
    Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:10 +0200
      Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() Len Brown <lenb@kernel.org> - 2017-06-17 02:40 +0200
        Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:50 +0200
          Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() Len Brown <lenb@kernel.org> - 2017-06-17 03:20 +0200
            Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 03:30 +0200
              Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() "Rafael J. Wysocki" <rafael@kernel.org> - 2017-06-17 03:50 +0200
                Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() Len Brown <lenb@kernel.org> - 2017-06-17 04:10 +0200
    Re: [PATCH 3/5] intel_pstate: remove intel_pstate.get() "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:40 +0200
  [PATCH 1/5] x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz" Len Brown <lenb@kernel.org> - 2017-06-08 04:50 +0200
  [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode. Len Brown <lenb@kernel.org> - 2017-06-08 04:50 +0200
    Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode. "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:20 +0200
      Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in  "performance" mode. Len Brown <lenb@kernel.org> - 2017-06-17 03:00 +0200
        Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode. "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 03:20 +0200
          Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in  "performance" mode. Len Brown <lenb@kernel.org> - 2017-06-17 03:40 +0200
          Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in  "performance" mode. Len Brown <lenb@kernel.org> - 2017-06-17 03:40 +0200
  [PATCH 5/5] intel_pstate: delete scheduler hook in HWP mode Len Brown <lenb@kernel.org> - 2017-06-08 04:50 +0200
    Re: [PATCH 5/5] intel_pstate: delete scheduler hook in HWP mode "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2017-06-17 02:20 +0200
      Re: [PATCH 5/5] intel_pstate: delete scheduler hook in HWP mode Len Brown <lenb@kernel.org> - 2017-06-17 03:30 +0200

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