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Subject[PATCH v1 2/5] cpuidle: menu: Record tick delta value in struct menu_device
Date
Since the tick delta is used in multiple places in menu_select(), it's
better to use single one variable to record this value; furthermore, for
more readable we can refactor the code to split a separate function to
making decision for stopping tick, which also needs to use tick delta
value as one metric for consideration.

To achieve these purposes, this patch adds a new item 'tick_delta_us' in
struct menu_device to record tick delta value. This patch also is a
preparation for optimization stopping tick in sequential patches.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
drivers/cpuidle/governors/menu.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b972db1..83618ab 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -124,6 +124,7 @@ struct menu_device {
int tick_wakeup;

unsigned int next_timer_us;
+ unsigned int tick_delta_us;
unsigned int predicted_us;
unsigned int bucket;
unsigned int correction_factor[BUCKETS];
@@ -305,6 +306,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,

/* determine the expected residency time, round up */
data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length(&delta_next));
+ data->tick_delta_us = ktime_to_us(delta_next);

get_iowait_load(&nr_iowaiters, &cpu_load);
data->bucket = which_bucket(data->next_timer_us, nr_iowaiters);
@@ -317,7 +319,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
* timer event for the idle state selection.
*/
if (tick_nohz_tick_stopped()) {
- data->predicted_us = ktime_to_us(delta_next);
+ data->predicted_us = data->tick_delta_us;
goto select;
}

@@ -400,11 +402,11 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
*/
if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) ||
data->predicted_us < TICK_USEC) && !tick_nohz_tick_stopped()) {
- unsigned int delta_next_us = ktime_to_us(delta_next);

*stop_tick = false;

- if (idx > 0 && drv->states[idx].target_residency > delta_next_us) {
+ if (idx > 0 &&
+ drv->states[idx].target_residency > data->tick_delta_us) {
/*
* The tick is not going to be stopped and the target
* residency of the state to be returned is not within
@@ -417,7 +419,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
continue;

idx = i;
- if (drv->states[i].target_residency <= delta_next_us)
+ if (drv->states[i].target_residency <=
+ data->tick_delta_us)
break;
}
}
--
2.7.4
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