On Wed, 20 Jan 2016, Daniel Lezcano wrote:
[...]

One more comment:

+		/*
+		 * If the mean value is null, just ignore this wakeup
+		 * source.
+		 */
+		mean = stats_mean(&w->stats);
+		if (!mean)
+			continue;
+
+		variance = stats_variance(&w->stats, mean);
+		/*
+		 * We want to check the last interval is:
+		 *
+		 *  mean - stddev < interval < mean + stddev
+		 *
+		 * That simplifies to:
+		 *
+		 * -stddev < interval - mean < stddev
+		 *
+		 * abs(interval - mean) < stddev
+		 *
+		 * The standard deviation is the sqrt of the variance:
+		 *
+		 * abs(interval - mean) < sqrt(variance)
+		 *
+		 * and we want to prevent to do an sqrt, so we square
+		 * the equation:
+		 *
+		 * (interval - mean)^2 < variance
+		 *
+		 * So if the latest value of the stats complies with
+		 * this condition, then the wakeup source is
+		 * considered predictable and can be used to predict
+		 * the next event.
+		 */
+		interval = w->stats.values[w->stats.w_ptr];
+		if ((u64)((interval - mean) * (interval - mean)) > variance)
+			continue;
+
+		/*
+		 * Let's compute the next event: the wakeup source is
+		 * considered predictable, we add the average interval
+		 * time added to the latest interruption event time.
+		 */
+		next = ktime_add_us(w->timestamp, stats_mean(&w->stats));

You don't need to call stats_mean() again as you have it in the 'mean' 
variable already.


Nicolas