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Subject[RFC PATCHC 2/3] idle: store the idle state the cpu is
Date
When the cpu enters idle it stores the cpuidle power info in the struct
rq which in turn could be used to take a right decision when balancing
a task.

As soon as the cpu exits the idle state, the structure is filled with the
NULL pointer.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
kernel/sched/idle.c | 17 +++++++++++++++--
kernel/sched/sched.h | 5 +++++
2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 8f4390a..5c32c11 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -12,6 +12,8 @@

#include <trace/events/power.h>

+#include "sched.h"
+
static int __read_mostly cpu_idle_force_poll;

void cpu_idle_poll_ctrl(bool enable)
@@ -69,7 +71,7 @@ void __weak arch_cpu_idle(void)
* NOTE: no locks or semaphores should be used here
* return non-zero on failure
*/
-static int cpuidle_idle_call(void)
+static int cpuidle_idle_call(struct cpuidle_power **power)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
@@ -143,6 +145,10 @@ static int cpuidle_idle_call(void)
if (!ret) {
trace_cpu_idle_rcuidle(next_state, dev->cpu);

+ *power = &drv->states[next_state].power;
+
+ wmb();
+
/*
* Enter the idle state previously
* returned by the governor
@@ -154,6 +160,10 @@ static int cpuidle_idle_call(void)
entered_state = cpuidle_enter(drv, dev,
next_state);

+ *power = NULL;
+
+ wmb();
+
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT,
dev->cpu);

@@ -198,6 +208,9 @@ static int cpuidle_idle_call(void)
*/
static void cpu_idle_loop(void)
{
+ struct rq *rq = this_rq();
+ struct cpuidle_power **power = &rq->power;
+
while (1) {
tick_nohz_idle_enter();

@@ -223,7 +236,7 @@ static void cpu_idle_loop(void)
if (cpu_idle_force_poll || tick_check_broadcast_expired())
cpu_idle_poll();
else
- cpuidle_idle_call();
+ cpuidle_idle_call(power);

arch_cpu_idle_exit();
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1929deb..1bcac35 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -14,6 +14,7 @@
#include "cpuacct.h"

struct rq;
+struct cpuidle_power;

extern __read_mostly int scheduler_running;

@@ -632,6 +633,10 @@ struct rq {
#ifdef CONFIG_SMP
struct llist_head wake_list;
#endif
+
+#ifdef CONFIG_CPU_IDLE
+ struct cpuidle_power *power;
+#endif
};

static inline int cpu_of(struct rq *rq)
--
1.7.9.5


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