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Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86

From Andi Kleen <ak@linux.intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86
Date 2017-05-22 22:10 +0200
Message-ID <tK1Oq-1JR-29@gated-at.bofh.it> (permalink)
References <tIUlY-5uX-11@gated-at.bofh.it> <tIUlY-5uX-17@gated-at.bofh.it> <tK0fD-HF-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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> 
> > The ref cycles always tick at their frequency, or slower when the system
> > is idling. That means the NMI watchdog can never expire too early,
> > unlike with cycles.
> >
> Just make the period longer, like 30% longer. Take the max turbo factor you can
> get and use that. It is okay if it takes longer of machine with
> smaller max Turbo ratios.

That would be a ticking time bomb. Turbo ratios are likely to grow.

There's no architectural way to get a turbo factor. Even if there
is a model specific MSR it would likely not work in virtualization etc.

You could make the timeout ridiculously large, but even that would
have a small chance of failure.

-Andi

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[PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter kan.liang@intel.com - 2017-05-19 20:00 +0200
  [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86 kan.liang@intel.com - 2017-05-19 20:00 +0200
    Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref  cycles on x86 Peter Zijlstra <peterz@infradead.org> - 2017-05-22 14:10 +0200
      Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref  cycles on x86 Peter Zijlstra <peterz@infradead.org> - 2017-05-22 14:10 +0200
      RE: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to  ref cycles on x86 "Liang, Kan" <kan.liang@intel.com> - 2017-05-22 19:00 +0200
        Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref  cycles on x86 Peter Zijlstra <peterz@infradead.org> - 2017-05-22 21:30 +0200
    Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref  cycles on x86 Stephane Eranian <eranian@google.com> - 2017-05-22 20:30 +0200
      Re: [PATCH 2/2] perf/x86/intel, watchdog: Switch NMI watchdog to ref  cycles on x86 Andi Kleen <ak@linux.intel.com> - 2017-05-22 22:10 +0200
  Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra <peterz@infradead.org> - 2017-05-22 10:40 +0200
    Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Stephane Eranian <eranian@google.com> - 2017-05-22 20:20 +0200
  Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra <peterz@infradead.org> - 2017-05-22 11:30 +0200
    Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra <peterz@infradead.org> - 2017-05-22 14:30 +0200
      RE: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter "Liang, Kan" <kan.liang@intel.com> - 2017-05-22 19:00 +0200
    RE: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter "Liang, Kan" <kan.liang@intel.com> - 2017-05-22 19:00 +0200
      Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra <peterz@infradead.org> - 2017-05-22 21:30 +0200
        Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Stephane Eranian <eranian@google.com> - 2017-05-22 21:30 +0200
          RE: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter "Liang, Kan" <kan.liang@intel.com> - 2017-05-23 00:00 +0200
          Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Peter Zijlstra <peterz@infradead.org> - 2017-05-23 08:40 +0200
            Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Stephane Eranian <eranian@google.com> - 2017-05-23 08:50 +0200
              Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Andi Kleen <ak@linux.intel.com> - 2017-05-24 17:50 +0200
                Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP  counter Vince Weaver <vincent.weaver@maine.edu> - 2017-05-24 18:10 +0200
                Re: [PATCH 1/2] perf/x86/intel: enable CPU ref_cycles for GP counter Andi Kleen <ak@linux.intel.com> - 2017-05-24 19:00 +0200

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