On Mon, 24 Feb 2014, Tuukka Tikkanen wrote: > The menu governor uses coefficients as one method of actual idle > period length estimation. The coefficients are, as detailed below, > multipliers giving expected idle period length from time until next > timer expiry. The multipliers are supposed to have domain of (0..1]. > > The coefficients are fractions where only the numerators are stored > and denominators are a shared constant RESOLUTION*DECAY. Since the > value of the coefficient should always be greater than 0 and less > than or equal to 1, the numerator must have a value greater than > 0 and less than or equal to RESOLUTION*DECAY. > > If the coefficients are updated with measured idle durations exceeding > timer length, the multiplier may reach values exceeding unity (i.e. > the stored numerator exceeds RESOLUTION*DECAY). This patch ensures that > the multipliers are updated with durations capped to timer length. > > Signed-off-by: Tuukka Tikkanen <tuukka.tikka...@linaro.org> Acked-by: Nicolas Pitre <n...@linaro.org>
> --- > drivers/cpuidle/governors/menu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/cpuidle/governors/menu.c > b/drivers/cpuidle/governors/menu.c > index 115386a..f0995dd 100644 > --- a/drivers/cpuidle/governors/menu.c > +++ b/drivers/cpuidle/governors/menu.c > @@ -410,6 +410,9 @@ static void menu_update(struct cpuidle_driver *drv, > struct cpuidle_device *dev) > if (measured_us > target->exit_latency) > measured_us -= target->exit_latency; > > + /* Make sure our coefficients do not exceed unity */ > + if (measured_us > data->next_timer_us) > + measured_us = data->next_timer_us; > > /* Update our correction ratio */ > new_factor = data->correction_factor[data->bucket]; > -- > 1.7.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
