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    SubjectRe: [linux-pm] [PATCH] cpuidle: avoid singing capacitors
    On Tue, 4 Mar 2008 11:01:28 -0800
    "Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com> wrote:

    > >
    > >(On that subject, does anyone except Adam understand that
    > >algorithm? Some comments wouldn't hurt...)
    >
    > Prediction is based on cumulative time till "non expected wakeup". So,
    > prediction will come into play only when there are very short wakeups
    > due to "unexpected wakeups".
    >

    Ah, so the measured_us and elapsed_us are trying to keep track of time between non-timer wakeups?

    > >So for now, I'm back to thinking that measuring the interval
    > >between deep sleeps is the better approach. I could use some
    > >ideas for a good clock source though. I haven't dug much
    > >deeper than jiffies when it comes to kernel timekeeping.
    >
    > I think best solution is to use get_last_residency that is already
    > there. If the last residency or expected_us is very low, you can avoid
    > deep idle states. That way you don't have to depend on jiffies being
    > updated at the time you are checking it.
    >

    I tried using predicted_us and last_measured_us, and those didn't work (see the #if 0 code in my last patch). And since cpuidle_get_last_residency() is part of predicted_us, I don't think it is reporting useful values.

    Rgds
    --
    -- Pierre Ossman

    Linux kernel, MMC maintainer http://www.kernel.org
    PulseAudio, core developer http://pulseaudio.org
    rdesktop, core developer http://www.rdesktop.org


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