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Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period
Date 2016-01-20 20:40 +0100
Message-ID <qT6LM-2E2-31@gated-at.bofh.it> (permalink)
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On Wed, Jan 20, 2016 at 02:17:57PM -0500, Nicolas Pitre wrote:
> > It is also a friggin pointless /1000. The cpuidle code also loves to do
> > this, and its silly, u64 add/sub are _way_ cheaper than u64 / 1000.
> 
> For the purpose of this code, nanoseconds simply provides too many bits 
> for what we care.  Computing the variance implies squared values.
> 
> *However* we can simply do diff = (timestamp - w->timestamp) >> 10 
> instead.  No need to have an exact microsecs base.

Right, you could also reduce bits at the variance computation, but yes.

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Re: [RFC PATCH 2/2] sched: idle: IRQ based next prediction for idle  period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-18 14:30 +0100
  Re: [RFC PATCH 2/2] sched: idle: IRQ based next prediction for idle  period Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 16:50 +0100
    [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-01-20 18:50 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 19:50 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 11:10 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:10 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-01-20 20:20 +0100
          Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:40 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:40 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:50 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-01-20 21:00 +0100
          Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Peter Zijlstra <peterz@infradead.org> - 2016-01-20 21:30 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 21:00 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 15:00 +0100
          Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Thomas Gleixner <tglx@linutronix.de> - 2016-01-21 15:20 +0100
    [RFC V2 0/2] IRQ based next prediction Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100
    [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100
      Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-01-20 21:20 +0100
        Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle  period Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 14:10 +0100
    [RFC V2 0/2] IRQ based next prediction Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100
      [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100
        Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 19:00 +0100
          Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 10:30 +0100
            Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-21 11:30 +0100
        Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:10 +0100
          Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 21:00 +0100
            Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-01-20 21:10 +0100
            Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Peter Zijlstra <peterz@infradead.org> - 2016-01-20 21:30 +0100
              Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-20 21:30 +0100
            Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 11:00 +0100
              Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Peter Zijlstra <peterz@infradead.org> - 2016-01-21 11:10 +0100
                Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 13:40 +0100
                Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-21 21:30 +0100
              Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-21 15:00 +0100
                Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 15:20 +0100
                Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2016-01-21 20:00 +0100
                Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Peter Zijlstra <peterz@infradead.org> - 2016-01-22 11:20 +0100
          Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 10:30 +0100
        Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Peter Zijlstra <peterz@infradead.org> - 2016-01-20 20:30 +0100
          Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-21 11:00 +0100
      [RFC V2 1/2] irq: Add a framework to measure interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2016-01-20 17:10 +0100

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