In previous version, cpu_pm_enter is invoked after the governor
select the state, which cause the executing time of cpu_pm_enter
is included in the idle time. Moving it before the state selection.
Please refer to bellowing chart for detailed information
current approach:
static void cpu_idle_loop(void)
{
while (1) {
tick_nohz_idle_enter();
--->__tick_nohz_idle_enter
--->tick_nohz_stop_sched_tick
{
...
ts->sleep_length = ktime_sub(dev->next_event, now);
/*1*/
...
}
while (!need_resched()) {
...
local_irq_disable();
arch_cpu_idle_enter();
--->idle_notifier_call_chain(IDLE_START);
/*2*/
cpuidle_idle_call();
--->next_state = cpuidle_select(drv, dev);
/*3*/
--->static int arm_enter_idle_state(...)
{
...
ret = cpu_pm_enter();
/*4*/
}
}
---------|----------------------|----------------------------|------------------------------------|--------------------------------------------|--------------------
1.now 2.IDLE_START 3.select idle state
4.CPU_PM_ENTER next_event
(sleep_length)
modified approach:
static void cpu_idle_loop(void)
{
while (1) {
tick_nohz_idle_enter();
--->__tick_nohz_idle_enter
--->tick_nohz_stop_sched_tick
{
...
...
}
while (!need_resched()) {
...
local_irq_disable();
arch_cpu_idle_enter();
--->idle_notifier_call_chain(IDLE_START);
/*1*/
cpuidle_idle_call();
--->ret = cpu_pm_enter();
/*2*/
--->tick_nohz_get_sleep_length
{
ts->sleep_length = ktime_sub(dev->next_event,
now); /*3*/
}
--->next_state = cpuidle_select(drv, dev);
/*4*/
--->static int arm_enter_idle_state(...)
}
----------------|---------------------------------------|---------------------|------------------|--------------------------------------------|--------------------
1.IDLE_START 2.CPU_PM_ENTER
3.now 4.select idle state next_event
(sleep_length)
Signed-off-by: Zhaoyang Huang <zhaoyang.hu...@spreadtrum.com>
---
kernel/sched/idle.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index bd12c6c..929da2e 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -5,6 +5,7 @@
#include <linux/cpu.h>
#include <linux/cpuidle.h>
#include <linux/cpuhotplug.h>
+#include <linux/cpu_pm.h>
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/stackprotector.h>
@@ -130,6 +131,7 @@ static void cpuidle_idle_call(void)
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
int next_state, entered_state;
+ int ret;
/*
* Check if the idle task must be rescheduled. If it is the
@@ -174,12 +176,16 @@ static void cpuidle_idle_call(void)
/*
* Ask the cpuidle framework to choose a convenient idle state.
*/
- next_state = cpuidle_select(drv, dev);
- entered_state = call_cpuidle(drv, dev, next_state);
- /*
- * Give the governor an opportunity to reflect on the outcome
- */
- cpuidle_reflect(dev, entered_state);
+ ret = cpu_pm_enter();
+ if (!ret) {
+ next_state = cpuidle_select(drv, dev);
+ entered_state = call_cpuidle(drv, dev, next_state);
+ cpu_pm_exit();
+ /*
+ * Give the governor an opportunity to reflect on the
outcome
+ */
+ cpuidle_reflect(dev, entered_state);
+ }
}
exit_idle:
--
1.9.1
