time: track accurate idle time with tick_sched.idle_sleeptime

Current idle time in kstat is based on jiffies and is coarse grained.
tick_sched.idle_sleeptime is making some attempt to keep track of idle time
in a fine grained manner.  But, it is not handling the time spent in
interrupts fully.

Make tick_sched.idle_sleeptime accurate with respect to time spent on
handling interrupts and also add tick_sched.idle_lastupdate, which keeps
track of last time when idle_sleeptime was updated.

This statistics will be crucial for cpufreq-ondemand governor, which can
shed some conservative gaurd band that is uses today while setting the
frequency.  The ondemand changes that uses the exact idle time is coming
soon.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/tick.h b/include/linux/tick.h
index f4a1395e05ff..0fadf95debe1 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -51,8 +51,10 @@ struct tick_sched {
         unsigned long                   idle_jiffies;
         unsigned long                   idle_calls;
         unsigned long                   idle_sleeps;
+        int                             idle_active;
         ktime_t                         idle_entrytime;
         ktime_t                         idle_sleeptime;
+        ktime_t                         idle_lastupdate;
         ktime_t                         sleep_length;
         unsigned long                   last_jiffies;
         unsigned long                   next_jiffies;
@@ -103,6 +105,8 @@ extern void tick_nohz_stop_sched_tick(void);
 extern void tick_nohz_restart_sched_tick(void);
 extern void tick_nohz_update_jiffies(void);
 extern ktime_t tick_nohz_get_sleep_length(void);
+extern void tick_nohz_stop_idle(int cpu);
+extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
 # else
 static inline void tick_nohz_stop_sched_tick(void) { }
 static inline void tick_nohz_restart_sched_tick(void) { }
@@ -113,6 +117,8 @@ static inline ktime_t tick_nohz_get_sleep_length(void)
 
         return len;
 }
+static inline void tick_nohz_stop_idle(int cpu) { }
+static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return 0; }
 # endif /* !NO_HZ */
 
 #endif