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Re: [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode.

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sorry, that was a premature send...

>>> > What about update_turbo_pstate()?
>>> >
>>> > In theory MSR_IA32_MISC_ENABLE_TURBO_DISABLE can be set at any time, so
>>> > wouldn't that become problematic after this change?
>>>
>>> yes, the sysfs "no_turbo" attribute can be modified at any time, invoking
>>> update_turbo_state(), which will update MSR_IA32_MISC_ENABLE_TURBO_DISABLE
>>
>> If that was the only way it could change, I wouldn't worry about it, but what
>> about changes by BMCs and similar?  Are they not a concern?
>>
>>> But how is the presence or change in turbo related to the lack of a
>>> need to hook the scheduler callback in "performance" mode?  The hook
>>> literally does nothing in this case, except consume cycles, no?
>>
>> No.
>>
>> It actually sets the P-state to the current maximum (which admittedly is
>> excessive) exactly because the maximum may change on the fly in theory.
>
> There are 2 cases.
>
> If turbo was enabled and were we requesting max turbo
> and "somebody" disabled turbo in an MSR, then the HW would
> simply clip our excessive
request to what the hardware supports.

if turbo was disabled and we were requesting max non-turbo,
and "somebody" enabled turbo in the MSR,
then it is highly likely that current request is already sufficiently
high enough
to enable turbo.  "highly likely" = would work on 100% of the
machines I have ever seen, including those with mis-configured TAR.

ie. it should not matter.

>> If it can't change on the fly (or we don't care), we can do some more
>> simplifications there. :-)
>
> I do not think it is Linux's responsibility to monitor changes to MSRs
> such as Turbo enable/disable done behind its back by a BMC at run-time.
> (if this is even possible)
>
>
> --
> Len Brown, Intel Open Source Technology Center

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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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