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Groups > linux.kernel > #1589020

Re: tip.today - scheduler bam boom crash (cpu hotplug)

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: tip.today - scheduler bam boom crash (cpu hotplug)
Date 2017-02-28 00:00 +0100
Message-ID <tfCqS-3Po-9@gated-at.bofh.it> (permalink)
References (4 earlier) <tfwls-86h-15@gated-at.bofh.it> <tfwv8-8at-13@gated-at.bofh.it> <tfxhv-jQ-9@gated-at.bofh.it> <tfxUe-Oq-11@gated-at.bofh.it> <tfyQh-1uW-11@gated-at.bofh.it>
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On Mon, Feb 27, 2017 at 02:06:27PM -0500, Paolo Bonzini wrote:
> > > +	if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
> > > +		mark_tsc_unstable("not invariant");
> > 
> > Errm, no.
> > 
> > That makes TSC unusable for systems which do not go into C/P states in
> > which the TSC stops. There is a world outside KVM ....
> 
> Actually I was surprised too by Peter's patch, as it was adding
> mark_tsc_unstable pretty much everywhere that didn't have nonstop TSC.
> But hopefully it would still be okay to call clear_sched_clock_stable
> in tsc_init, in the same way.

I was preserving the sched_clock behaviour. That said, maybe we can
simply remove all those extra checks and only rely on the current
mark_tsc_unstable() calls.

I'll just have to sit down and consider the various cases..

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Thread

Re: tip.today - scheduler bam boom crash (cpu hotplug) Wanpeng Li <kernellwp@gmail.com> - 2017-02-27 13:40 +0100
  Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-27 13:50 +0100
    Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 14:00 +0100
      Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 16:40 +0100
        Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 17:30 +0100
          Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-27 17:40 +0100
            Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 18:30 +0100
              Re: tip.today - scheduler bam boom crash (cpu hotplug) Thomas Gleixner <tglx@linutronix.de> - 2017-02-27 19:10 +0100
                Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 20:10 +0100
                Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-28 00:00 +0100
          Re: tip.today - scheduler bam boom crash (cpu hotplug) Wanpeng Li <kernellwp@gmail.com> - 2017-02-28 03:00 +0100
            Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-28 09:10 +0100
              Re: tip.today - scheduler bam boom crash (cpu hotplug) Wanpeng Li <kernellwp@gmail.com> - 2017-02-28 09:20 +0100
        Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-27 17:50 +0100
      Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-27 23:50 +0100
    Re: tip.today - scheduler bam boom crash (cpu hotplug) Wanpeng Li <kernellwp@gmail.com> - 2017-02-27 15:00 +0100
      Re: tip.today - scheduler bam boom crash (cpu hotplug) Peter Zijlstra <peterz@infradead.org> - 2017-02-27 15:50 +0100
  Re: tip.today - scheduler bam boom crash (cpu hotplug) Paolo Bonzini <pbonzini@redhat.com> - 2017-02-27 16:10 +0100

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