===================================================================
@@ -19,6 +19,8 @@
#include <linux/sched/stat.h>
#include <linux/math64.h>
+#include "gov.h"
+
#define BUCKETS 12
#define INTERVAL_SHIFT 3
#define INTERVALS (1UL << INTERVAL_SHIFT)
@@ -166,8 +168,7 @@ static void menu_update(struct cpuidle_d
* of points is below a threshold. If it is... then use the
* average of these 8 points as the estimated value.
*/
-static unsigned int get_typical_interval(struct menu_device *data,
- unsigned int predicted_us)
+static unsigned int get_typical_interval(struct menu_device *data)
{
int i, divisor;
unsigned int min, max, thresh, avg;
@@ -195,13 +196,6 @@ again:
}
}
- /*
- * If the result of the computation is going to be discarded anyway,
- * avoid the computation altogether.
- */
- if (min >= predicted_us)
- return UINT_MAX;
-
if (divisor == INTERVALS)
avg = sum >> INTERVAL_SHIFT;
else
@@ -267,7 +261,6 @@ static int menu_select(struct cpuidle_dr
{
struct menu_device *data = this_cpu_ptr(&menu_devices);
s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
- unsigned int predicted_us;
u64 predicted_ns;
u64 interactivity_req;
unsigned int nr_iowaiters;
@@ -279,16 +272,41 @@ static int menu_select(struct cpuidle_dr
data->needs_update = 0;
}
- /* determine the expected residency time, round up */
- delta = tick_nohz_get_sleep_length(&delta_tick);
- if (unlikely(delta < 0)) {
- delta = 0;
- delta_tick = 0;
- }
- data->next_timer_ns = delta;
-
nr_iowaiters = nr_iowait_cpu(dev->cpu);
- data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
+
+ /* Find the shortest expected idle interval. */
+ predicted_ns = get_typical_interval(data) * NSEC_PER_USEC;
+ if (predicted_ns > RESIDENCY_THRESHOLD_NS) {
+ unsigned int timer_us;
+
+ /* Determine the time till the closest timer. */
+ delta = tick_nohz_get_sleep_length(&delta_tick);
+ if (unlikely(delta < 0)) {
+ delta = 0;
+ delta_tick = 0;
+ }
+
+ data->next_timer_ns = delta;
+ data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
+
+ /* Round up the result for half microseconds. */
+ timer_us = div_u64((RESOLUTION * DECAY * NSEC_PER_USEC) / 2 +
+ data->next_timer_ns *
+ data->correction_factor[data->bucket],
+ RESOLUTION * DECAY * NSEC_PER_USEC);
+ /* Use the lowest expected idle interval to pick the idle state. */
+ predicted_ns = min((u64)timer_us * NSEC_PER_USEC, predicted_ns);
+ } else {
+ /*
+ * Because the next timer event is not going to be determined
+ * in this case, assume that without the tick the closest timer
+ * will be in distant future and that the closest tick will occur
+ * after 1/2 of the tick period.
+ */
+ data->next_timer_ns = KTIME_MAX;
+ delta_tick = TICK_NSEC / 2;
+ data->bucket = which_bucket(KTIME_MAX, nr_iowaiters);
+ }
if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
((data->next_timer_ns < drv->states[1].target_residency_ns ||
@@ -303,16 +321,6 @@ static int menu_select(struct cpuidle_dr
return 0;
}
- /* Round up the result for half microseconds. */
- predicted_us = div_u64(data->next_timer_ns *
- data->correction_factor[data->bucket] +
- (RESOLUTION * DECAY * NSEC_PER_USEC) / 2,
- RESOLUTION * DECAY * NSEC_PER_USEC);
- /* Use the lowest expected idle interval to pick the idle state. */
- predicted_ns = (u64)min(predicted_us,
- get_typical_interval(data, predicted_us)) *
- NSEC_PER_USEC;
-
if (tick_nohz_tick_stopped()) {
/*
* If the tick is already stopped, the cost of possible short
===================================================================
@@ -140,6 +140,8 @@
#include <linux/sched/topology.h>
#include <linux/tick.h>
+#include "gov.h"
+
/*
* The number of bits to shift the CPU's capacity by in order to determine
* the utilized threshold.
===================================================================
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Common definitions for cpuidle governors. */
+
+#ifndef __CPUIDLE_GOVERNOR_H
+#define __CPUIDLE_GOVERNOR_H
+
+/*
+ * Idle state target residency threshold used for deciding whether or not to
+ * check the time till the closest expected timer event.
+ */
+#define RESIDENCY_THRESHOLD_NS (15 * NSEC_PER_USEC)
+
+#endif /* __CPUIDLE_GOVERNOR_H */