On Sun, Nov 04, 2018 at 05:31:20PM +0100, Rafael J. Wysocki wrote:
> + * - If there is a pattern of 5 or more recent non-timer wakeups earlier than
> + * the closest timer event, expect one more of them to occur and use the
> + * average of the idle duration values corresponding to them to select an
> + * idle state for the CPU.
> +/**
> + * teo_idle_duration - Estimate the duration of the upcoming CPU idle time.
> + * @drv: cpuidle driver containing state data.
> + * @cpu_data: Governor data for the target CPU.
> + * @sleep_length_us: Time till the closest timer event in microseconds.
> + */
> +unsigned int teo_idle_duration(struct cpuidle_driver *drv,
> + struct teo_cpu *cpu_data,
> + unsigned int sleep_length_us)
> +{
> + u64 range, max_spread, max, sum;
> + unsigned int count;
> +
> + /*
> + * If the sleep length is below the target residency of idle state 1,
> + * the only viable choice is to select the first available (enabled)
> + * idle state, so return immediately in that case.
> + */
> + if (sleep_length_us < drv->states[1].target_residency)
> + return sleep_length_us;
> +
> + /*
> + * The purpose of this function is to check if there is a pattern of
> + * wakeups indicating that it would be better to select a state
> + * shallower than the deepest one matching the sleep length or the
> + * deepest one at all if the sleep lenght is long. Larger idle duration
> + * values are beyond the interesting range.
> + *
> + * Narrowing the range of interesting values down upfront also helps to
> + * avoid overflows during the computation below.
> + */
> + range = drv->states[drv->state_count-1].target_residency;
> + range = min_t(u64, sleep_length_us, range + (range >> 2));
> +
> + /*
> + * This is the value to compare with the distance between the average
> + * and the greatest sample to decide whether or not it is small enough.
> + * Take 10 us as the total cap of it.
> + */
> + max_spread = max_t(u64, range >> MAX_SPREAD_SHIFT, 10);
> +
> + max = range;
> +
> + do {
> + u64 cap = max;
> + int i;
> +
> + /*
> + * Compute the sum of the saved intervals below the cap and the
> + * sum of of their squares. Count them and find the maximum
> + * interval below the cap.
> + */
> + count = 0;
> + sum = 0;
> + max = 0;
> +
> + for (i = 0; i < INTERVALS; i++) {
> + u64 val = cpu_data->intervals[i];
> +
> + if (val >= cap)
> + continue;
> +
> + count++;
> + sum += val;
> + if (max < val)
> + max = val;
> + }
> +
> + /*
> + * Give up if the total number of interesting samples is too
> + * small.
> + */
> + if (cap == range && count <= INTERVALS / 2)
> + return sleep_length_us;
> +
> + /*
> + * If the distance between the max and the average is too large,
> + * discard the max an repeat.
> + */
> + } while (count > 3 && max > max_spread && (max - max_spread) * count >
> sum);
> +
> + return div64_u64(sum, count);
> +}
Instead of this detector; why haven't you used the code from
kernel/irq/timings.c ?
