On Tue, Dec 16, 2014 at 8:52 AM, Len Brown <lenb@xxxxxxxxxx> wrote:
> From: Len Brown <len.brown@xxxxxxxxx>
>
> When menu sees CPUIDLE_FLAG_TIME_INVALID, it ignores its timestamps,
> and assumes that idle lasted as long as the time till next predicted
> timer expiration.
>
> But if an interrupt was seen and serviced before that duration,
> it would actually be more accurate to use the measured time
> rather than rounding up to the next predicted timer expiration.
>
> And if an interrupt is seen and serviced such that the mesured time
> exceeds the time till next predicted timer expiration, then
> truncating to that expiration is the right thing to do --
> since we can never stay idle past that timer expiration.
>
> So the code can do a better job without
> checking for CPUIDLE_FLAG_TIME_INVALID.
>
> Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Reviewed-by: Tuukka Tikkanen <tuukka.tikkanen@xxxxxxxxxx>
> ---
> drivers/cpuidle/governors/menu.c | 25 ++++++++++---------------
> 1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index 659d7b0..4058079 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -396,8 +396,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
> * power state and occurrence of the wakeup event.
> *
> * If the entered idle state didn't support residency measurements,
> - * we are basically lost in the dark how much time passed.
> - * As a compromise, assume we slept for the whole expected time.
> + * we use them anyway if they are short, and if long,
> + * truncate to the whole expected time.
> *
> * Any measured amount of time will include the exit latency.
> * Since we are interested in when the wakeup begun, not when it
> @@ -405,22 +405,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
> * the measured amount of time is less than the exit latency,
> * assume the state was never reached and the exit latency is 0.
> */
> - if (unlikely(target->flags & CPUIDLE_FLAG_TIME_INVALID)) {
> - /* Use timer value as is */
> - measured_us = data->next_timer_us;
>
> - } else {
> - /* Use measured value */
> - measured_us = cpuidle_get_last_residency(dev);
> + /* measured value */
> + measured_us = cpuidle_get_last_residency(dev);
>
> - /* Deduct exit latency */
> - if (measured_us > target->exit_latency)
> - measured_us -= target->exit_latency;
> + /* Deduct exit latency */
> + 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;
> - }
> + /* 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];
> --
> 2.1.2.451.g98349e5
>
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