[RFC PATCH v1 08/11] cpuidle: menu: remove reduplicative implementation

Aubrey Li
2017-07-10T01:50:07Z

From: Aubrey Li <aubrey.li@linux.intel.com>

For what cpuidle governor already does, we remove them from menu governor
---
drivers/cpuidle/governors/menu.c | 163 ---------------------------------------
1 file changed, 163 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b2330fd..f90c1a8 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -122,7 +122,6 @@

struct menu_device {
int last_state_idx;
- int needs_update;

unsigned int next_timer_us;
unsigned int predicted_us;
@@ -190,91 +189,6 @@ static inline int performance_multiplier(unsigned long nr_iowaiters, unsigned lo

static DEFINE_PER_CPU(struct menu_device, menu_devices);

-static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev);
-
-/*
- * Try detecting repeating patterns by keeping track of the last 8
- * intervals, and checking if the standard deviation of that set
- * 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)
-{
- int i, divisor;
- unsigned int max, thresh, avg;
- uint64_t sum, variance;
-
- thresh = UINT_MAX; /* Discard outliers above this value */
-
-again:
-
- /* First calculate the average of past intervals */
- max = 0;
- sum = 0;
- divisor = 0;
- for (i = 0; i < INTERVALS; i++) {
- unsigned int value = data->intervals[i];
- if (value <= thresh) {
- sum += value;
- divisor++;
- if (value > max)
- max = value;
- }
- }
- if (divisor == INTERVALS)
- avg = sum >> INTERVAL_SHIFT;
- else
- avg = div_u64(sum, divisor);
-
- /* Then try to determine variance */
- variance = 0;
- for (i = 0; i < INTERVALS; i++) {
- unsigned int value = data->intervals[i];
- if (value <= thresh) {
- int64_t diff = (int64_t)value - avg;
- variance += diff * diff;
- }
- }
- if (divisor == INTERVALS)
- variance >>= INTERVAL_SHIFT;
- else
- do_div(variance, divisor);
-
- /*
- * The typical interval is obtained when standard deviation is
- * small (stddev <= 20 us, variance <= 400 us^2) or standard
- * deviation is small compared to the average interval (avg >
- * 6*stddev, avg^2 > 36*variance). The average is smaller than
- * UINT_MAX aka U32_MAX, so computing its square does not
- * overflow a u64. We simply reject this candidate average if
- * the standard deviation is greater than 715 s (which is
- * rather unlikely).
- *
- * Use this result only if there is no timer to wake us up sooner.
- */
- if (likely(variance <= U64_MAX/36)) {
- if ((((u64)avg*avg > variance*36) && (divisor * 4 >= INTERVALS * 3))
- || variance <= 400) {
- return avg;
- }
- }
-
- /*
- * 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.
- */
- if ((divisor * 4) <= INTERVALS * 3)
- return UINT_MAX;
-
- thresh = max - 1;
- goto again;
-}
-
/**
* menu_select - selects the next idle state to enter
* @drv: cpuidle driver containing state data
@@ -291,11 +205,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
unsigned long nr_iowaiters, cpu_load;
int resume_latency = dev_pm_qos_raw_read_value(device);

- if (data->needs_update) {
- menu_update(drv, dev);
- data->needs_update = 0;
- }
-
/* resume_latency is 0 means no restriction */
if (resume_latency && resume_latency < latency_req)
latency_req = resume_latency;
@@ -389,78 +298,6 @@ static void menu_reflect(struct cpuidle_device *dev, int index)
struct menu_device *data = this_cpu_ptr(&menu_devices);

data->last_state_idx = index;
- data->needs_update = 1;
-}
-
-/**
- * menu_update - attempts to guess what happened after entry
- * @drv: cpuidle driver containing state data
- * @dev: the CPU
- */
-static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
-{
- struct menu_device *data = this_cpu_ptr(&menu_devices);
- int last_idx = data->last_state_idx;
- struct cpuidle_state *target = &drv->states[last_idx];
- unsigned int measured_us;
- unsigned int new_factor;
-
- /*
- * Try to figure out how much time passed between entry to low
- * power state and occurrence of the wakeup event.
- *
- * If the entered idle state didn't support residency measurements,
- * 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
- * was completed, we must subtract the exit latency. However, if
- * the measured amount of time is less than the exit latency,
- * assume the state was never reached and the exit latency is 0.
- */
-
- /* measured value */
- measured_us = cpuidle_get_last_residency(dev);
-
- /* Deduct exit latency */
- if (measured_us > 2 * target->exit_latency)
- measured_us -= target->exit_latency;
- else
- measured_us /= 2;
-
- /* 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];
- new_factor -= new_factor / DECAY;
-
- if (data->next_timer_us > 0 && measured_us < MAX_INTERESTING)
- new_factor += RESOLUTION * measured_us / data->next_timer_us;
- else
- /*
- * we were idle so long that we count it as a perfect
- * prediction
- */
- new_factor += RESOLUTION;
-
- /*
- * We don't want 0 as factor; we always want at least
- * a tiny bit of estimated time. Fortunately, due to rounding,
- * new_factor will stay nonzero regardless of measured_us values
- * and the compiler can eliminate this test as long as DECAY > 1.
- */
- if (DECAY == 1 && unlikely(new_factor == 0))
- new_factor = 1;
-
- data->correction_factor[data->bucket] = new_factor;
-
- /* update the repeating-pattern data */
- data->intervals[data->interval_ptr++] = measured_us;
- if (data->interval_ptr >= INTERVALS)
- data->interval_ptr = 0;
}

/**
--
2.7.4