[RFC PATCH v2 1/8] cpuidle: menu: extract prediction functionality

Aubrey Li
2017-09-30T07:21:35Z

There are several factors in the menu governor to predict the next
idle interval:
- the next timer
- the recent idle interval history
- the corrected idle interval pattern
These factors are common enough to be extracted to be one function.

Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
---
drivers/cpuidle/governors/menu.c | 64 +++++++++++++++++++++++++---------------
1 file changed, 40 insertions(+), 24 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 61b64c2..6bed197 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -276,6 +276,45 @@ static unsigned int get_typical_interval(struct menu_device *data)
}

/**
+ * menu_predict - predict the coming idle interval
+ *
+ * Return the predicted coming idle interval in micro-second
+ */
+static unsigned int menu_predict(void)
+{
+ struct menu_device *data = this_cpu_ptr(&menu_devices);
+ unsigned int expected_interval;
+ int cpu = smp_processor_id();
+
+ if (!data)
+ return UINT_MAX;
+
+ /* determine the expected residency time, round up */
+ data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length());
+
+ data->bucket = which_bucket(data->next_timer_us, nr_iowait_cpu(cpu));
+
+ /*
+ * Force the result of multiplication to be 64 bits even if both
+ * operands are 32 bits.
+ * Make sure to round up for half microseconds.
+ */
+ data->predicted_us = DIV_ROUND_CLOSEST_ULL((uint64_t)
+ data->next_timer_us * data->correction_factor[data->bucket],
+ RESOLUTION * DECAY);
+
+ expected_interval = get_typical_interval(data);
+ expected_interval = min(expected_interval, data->next_timer_us);
+
+ /*
+ * Use the lowest expected idle interval to pick the idle state.
+ */
+ data->predicted_us = min(data->predicted_us, expected_interval);
+
+ return data->predicted_us;
+}
+
+/**
* menu_select - selects the next idle state to enter
* @drv: cpuidle driver containing state data
* @dev: the CPU
@@ -289,7 +328,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
int first_idx;
int idx;
unsigned int interactivity_req;
- unsigned int expected_interval;
unsigned long nr_iowaiters, cpu_load;
int resume_latency = dev_pm_qos_raw_read_value(device);

@@ -306,24 +344,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
if (unlikely(latency_req == 0))
return 0;

- /* determine the expected residency time, round up */
- data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length());
-
- get_iowait_load(&nr_iowaiters, &cpu_load);
- data->bucket = which_bucket(data->next_timer_us, nr_iowaiters);
-
- /*
- * Force the result of multiplication to be 64 bits even if both
- * operands are 32 bits.
- * Make sure to round up for half microseconds.
- */
- data->predicted_us = DIV_ROUND_CLOSEST_ULL((uint64_t)data->next_timer_us *
- data->correction_factor[data->bucket],
- RESOLUTION * DECAY);
-
- expected_interval = get_typical_interval(data);
- expected_interval = min(expected_interval, data->next_timer_us);
-
if (CPUIDLE_DRIVER_STATE_START > 0) {
struct cpuidle_state *s = &drv->states[CPUIDLE_DRIVER_STATE_START];
unsigned int polling_threshold;
@@ -345,14 +365,10 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
}

/*
- * Use the lowest expected idle interval to pick the idle state.
- */
- data->predicted_us = min(data->predicted_us, expected_interval);
-
- /*
* Use the performance multiplier and the user-configurable
* latency_req to determine the maximum exit latency.
*/
+ get_iowait_load(&nr_iowaiters, &cpu_load);
interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load);
if (latency_req > interactivity_req)
latency_req = interactivity_req;
--
2.7.4