tick-sched: add more debug information

To allow better diagnosis of tick-sched related, especially NOHZ
related problems, we need to know when the last wakeup via an irq
happened and when the CPU left the idle state.

Add two fields (idle_waketime, idle_exittime) to the tick_sched
structure and add them to the timer_list output.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 0fadf95debe1f3a1b6415623926fc884fbc719ac..a881c652f7e925cb8e3d2f296c492800c3f163eb 100644 (file)
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -39,6 +39,8 @@ enum tick_nohz_mode {
  * @idle_calls:                Total number of idle calls
  * @idle_sleeps:       Number of idle calls, where the sched tick was stopped
  * @idle_entrytime:    Time when the idle call was entered
+ * @idle_waketime:     Time when the idle was interrupted
+ * @idle_exittime:     Time when the idle state was left
  * @idle_sleeptime:    Sum of the time slept in idle with sched tick stopped
  * @sleep_length:      Duration of the current idle sleep
  */
@@ -53,6 +55,8 @@ struct tick_sched {
        unsigned long                   idle_sleeps;
        int                             idle_active;
        ktime_t                         idle_entrytime;
+       ktime_t                         idle_waketime;
+       ktime_t                         idle_exittime;
        ktime_t                         idle_sleeptime;
        ktime_t                         idle_lastupdate;
        ktime_t                         sleep_length;

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 63f24b55069551f4331f09c090657b66be139f7e..88267f0a84713082dfb8ca719a76337b69990f04 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -137,6 +137,7 @@ void tick_nohz_update_jiffies(void)
 
        cpu_clear(cpu, nohz_cpu_mask);
        now = ktime_get();
+       ts->idle_waketime = now;
 
        local_irq_save(flags);
        tick_do_update_jiffies64(now);
@@ -400,6 +401,7 @@ void tick_nohz_restart_sched_tick(void)
         * Cancel the scheduled timer and restore the tick
         */
        ts->tick_stopped  = 0;
+       ts->idle_exittime = now;
        hrtimer_cancel(&ts->sched_timer);
        ts->sched_timer.expires = ts->idle_tick;
 

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 12c5f4cb6b8c67bd9d04bc8784989a2be9185fc1..d3d94c1a0fd2600a5c8d17b1b90801b449f880df 100644 (file)
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -166,6 +166,8 @@ static void print_cpu(struct seq_file *m, int cpu, u64 now)
                P(idle_calls);
                P(idle_sleeps);
                P_ns(idle_entrytime);
+               P_ns(idle_waketime);
+               P_ns(idle_exittime);
                P_ns(idle_sleeptime);
                P(last_jiffies);
                P(next_jiffies);