* of points is below a threshold. If it is... then use the
* average of these 8 points as the estimated value.
*/
-static int detect_repeating_patterns(struct menu_device *data)
+static u32 get_typical_interval(struct menu_device *data)
{
- int i;
- uint64_t avg = 0;
- uint64_t stddev = 0; /* contains the square of the std deviation */
- int ret = 0;
-
- /* first calculate average and standard deviation of the past */
- for (i = 0; i < INTERVALS; i++)
- avg += data->intervals[i];
- avg = avg / INTERVALS;
+ int i = 0, divisor = 0;
+ uint64_t max = 0, avg = 0, stddev = 0;
+ int64_t thresh = LLONG_MAX; /* Discard outliers above this value. */
+ unsigned int ret = 0;
- /* if the avg is beyond the known next tick, it's worthless */
- if (avg > data->expected_us)
- return 0;
-
- for (i = 0; i < INTERVALS; i++)
- stddev += (data->intervals[i] - avg) *
- (data->intervals[i] - avg);
+again:
- stddev = stddev / INTERVALS;
+ /* first calculate average and standard deviation of the past */
+ max = avg = divisor = stddev = 0;
+ for (i = 0; i < INTERVALS; i++) {
+ int64_t value = data->intervals[i];
+ if (value <= thresh) {
+ avg += value;
+ divisor++;
+ if (value > max)
+ max = value;
+ }
+ }
+ do_div(avg, divisor);
+ for (i = 0; i < INTERVALS; i++) {
+ int64_t value = data->intervals[i];
+ if (value <= thresh) {
+ int64_t diff = value - avg;
+ stddev += diff * diff;
+ }
+ }
+ do_div(stddev, divisor);
+ stddev = int_sqrt(stddev);
/*
- * now.. if stddev is small.. then assume we have a
- * repeating pattern and predict we keep doing this.
+ * If we have outliers to the upside in our distribution, discard
+ * those by setting the threshold to exclude these outliers, then
+ * calculate the average and standard deviation again. Once we get
+ * down to the bottom 3/4 of our samples, stop excluding samples.
+ *
+ * This can deal with workloads that have long pauses interspersed
+ * with sporadic activity with a bunch of short pauses.
+ *
+ * The typical interval is obtained when standard deviation is small
+ * or standard deviation is small compared to the average interval.
*/
-
- if (avg && stddev < STDDEV_THRESH) {
+ if (((avg > stddev * 6) && (divisor * 4 >= INTERVALS * 3))
+ || stddev <= 20) {
data->predicted_us = avg;
ret = 1;
+ return ret;
+
+ } else if ((divisor * 4) > INTERVALS * 3) {
+ /* Exclude the max interval */
+ thresh = max - 1;
+ goto again;
}
return ret;
data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket],
RESOLUTION * DECAY);
- repeat = detect_repeating_patterns(data);
+ repeat = get_typical_interval(data);
/*
* We want to default to C1 (hlt), not to busy polling