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>
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@ -51,8 +51,10 @@ struct tick_sched {
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unsigned long idle_jiffies;
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unsigned long idle_calls;
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unsigned long idle_sleeps;
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int idle_active;
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ktime_t idle_entrytime;
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ktime_t idle_sleeptime;
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ktime_t idle_lastupdate;
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ktime_t sleep_length;
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unsigned long last_jiffies;
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unsigned long next_jiffies;
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@ -103,6 +105,8 @@ extern void tick_nohz_stop_sched_tick(void);
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extern void tick_nohz_restart_sched_tick(void);
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extern void tick_nohz_update_jiffies(void);
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extern ktime_t tick_nohz_get_sleep_length(void);
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extern void tick_nohz_stop_idle(int cpu);
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extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
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# else
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static inline void tick_nohz_stop_sched_tick(void) { }
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static inline void tick_nohz_restart_sched_tick(void) { }
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@ -113,6 +117,8 @@ static inline ktime_t tick_nohz_get_sleep_length(void)
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return len;
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}
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static inline void tick_nohz_stop_idle(int cpu) { }
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static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return 0; }
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# endif /* !NO_HZ */
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#endif
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@ -280,9 +280,14 @@ asmlinkage void do_softirq(void)
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*/
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void irq_enter(void)
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{
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#ifdef CONFIG_NO_HZ
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int cpu = smp_processor_id();
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if (idle_cpu(cpu) && !in_interrupt())
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tick_nohz_stop_idle(cpu);
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#endif
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__irq_enter();
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#ifdef CONFIG_NO_HZ
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if (idle_cpu(smp_processor_id()))
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if (idle_cpu(cpu))
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tick_nohz_update_jiffies();
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#endif
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}
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@ -143,6 +143,44 @@ void tick_nohz_update_jiffies(void)
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local_irq_restore(flags);
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}
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void tick_nohz_stop_idle(int cpu)
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{
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struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
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if (ts->idle_active) {
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ktime_t now, delta;
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now = ktime_get();
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delta = ktime_sub(now, ts->idle_entrytime);
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ts->idle_lastupdate = now;
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ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
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ts->idle_active = 0;
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}
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}
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static ktime_t tick_nohz_start_idle(int cpu)
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{
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struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
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ktime_t now, delta;
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now = ktime_get();
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if (ts->idle_active) {
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delta = ktime_sub(now, ts->idle_entrytime);
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ts->idle_lastupdate = now;
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ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
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}
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ts->idle_entrytime = now;
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ts->idle_active = 1;
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return now;
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}
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u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
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{
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struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
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*last_update_time = ktime_to_us(ts->idle_lastupdate);
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return ktime_to_us(ts->idle_sleeptime);
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}
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/**
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* tick_nohz_stop_sched_tick - stop the idle tick from the idle task
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*
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@ -155,13 +193,14 @@ void tick_nohz_stop_sched_tick(void)
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unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags;
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unsigned long rt_jiffies;
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struct tick_sched *ts;
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ktime_t last_update, expires, now, delta;
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ktime_t last_update, expires, now;
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struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
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int cpu;
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local_irq_save(flags);
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cpu = smp_processor_id();
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now = tick_nohz_start_idle(cpu);
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ts = &per_cpu(tick_cpu_sched, cpu);
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/*
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@ -193,19 +232,7 @@ void tick_nohz_stop_sched_tick(void)
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}
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}
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now = ktime_get();
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/*
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* When called from irq_exit we need to account the idle sleep time
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* correctly.
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*/
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if (ts->tick_stopped) {
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delta = ktime_sub(now, ts->idle_entrytime);
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ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
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}
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ts->idle_entrytime = now;
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ts->idle_calls++;
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/* Read jiffies and the time when jiffies were updated last */
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do {
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seq = read_seqbegin(&xtime_lock);
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@ -337,23 +364,22 @@ void tick_nohz_restart_sched_tick(void)
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int cpu = smp_processor_id();
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struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
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unsigned long ticks;
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ktime_t now, delta;
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if (!ts->tick_stopped)
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return;
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/* Update jiffies first */
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now = ktime_get();
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ktime_t now;
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local_irq_disable();
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tick_nohz_stop_idle(cpu);
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if (!ts->tick_stopped) {
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local_irq_enable();
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return;
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}
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/* Update jiffies first */
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select_nohz_load_balancer(0);
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now = ktime_get();
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tick_do_update_jiffies64(now);
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cpu_clear(cpu, nohz_cpu_mask);
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/* Account the idle time */
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delta = ktime_sub(now, ts->idle_entrytime);
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ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
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/*
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* We stopped the tick in idle. Update process times would miss the
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* time we slept as update_process_times does only a 1 tick
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