* value. We do this unconditionally on any cpu, as we don't know whether the
* cpu, which has the update task assigned is in a long sleep.
*/
-void tick_nohz_update_jiffies(void)
+static void tick_nohz_update_jiffies(ktime_t now)
{
int cpu = smp_processor_id();
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
unsigned long flags;
- ktime_t now;
-
- if (!ts->tick_stopped)
- return;
- cpu_clear(cpu, nohz_cpu_mask);
- now = ktime_get();
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
ts->idle_waketime = now;
local_irq_save(flags);
touch_softlockup_watchdog();
}
-static void tick_nohz_stop_idle(int cpu)
+static void tick_nohz_stop_idle(int cpu, ktime_t now)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t delta;
- if (ts->idle_active) {
- ktime_t now, delta;
- now = ktime_get();
- delta = ktime_sub(now, ts->idle_entrytime);
- ts->idle_lastupdate = now;
- ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
- ts->idle_active = 0;
+ delta = ktime_sub(now, ts->idle_entrytime);
+ ts->idle_lastupdate = now;
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+ ts->idle_active = 0;
- sched_clock_idle_wakeup_event(0);
- }
+ sched_clock_idle_wakeup_event(0);
}
static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
return now;
}
+/**
+ * get_cpu_idle_time_us - get the total idle time of a cpu
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in
+ *
+ * Return the cummulative idle time (since boot) for a given
+ * CPU, in microseconds. The idle time returned includes
+ * the iowait time (unlike what "top" and co report).
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
+ */
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
struct tick_sched *ts;
ktime_t last_update, expires, now;
struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
+ u64 time_delta;
int cpu;
local_irq_save(flags);
cpu = smp_processor_id();
ts = &per_cpu(tick_cpu_sched, cpu);
+
+ /*
+ * Call to tick_nohz_start_idle stops the last_update_time from being
+ * updated. Thus, it must not be called in the event we are called from
+ * irq_exit() with the prior state different than idle.
+ */
+ if (!inidle && !ts->inidle)
+ goto end;
+
+ /*
+ * Set ts->inidle unconditionally. Even if the system did not
+ * switch to NOHZ mode the cpu frequency governers rely on the
+ * update of the idle time accounting in tick_nohz_start_idle().
+ */
+ ts->inidle = 1;
+
now = tick_nohz_start_idle(ts);
/*
if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
goto end;
- if (!inidle && !ts->inidle)
- goto end;
-
- ts->inidle = 1;
-
if (need_resched())
goto end;
if (ratelimit < 10) {
printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
- local_softirq_pending());
+ (unsigned int) local_softirq_pending());
ratelimit++;
}
goto end;
}
+ if (nohz_ratelimit(cpu))
+ goto end;
+
ts->idle_calls++;
/* Read jiffies and the time when jiffies were updated last */
do {
seq = read_seqbegin(&xtime_lock);
last_update = last_jiffies_update;
last_jiffies = jiffies;
+ time_delta = timekeeping_max_deferment();
} while (read_seqretry(&xtime_lock, seq));
- /* Get the next timer wheel timer */
- next_jiffies = get_next_timer_interrupt(last_jiffies);
- delta_jiffies = next_jiffies - last_jiffies;
-
- if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
+ if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
+ arch_needs_cpu(cpu)) {
+ next_jiffies = last_jiffies + 1;
delta_jiffies = 1;
+ } else {
+ /* Get the next timer wheel timer */
+ next_jiffies = get_next_timer_interrupt(last_jiffies);
+ delta_jiffies = next_jiffies - last_jiffies;
+ }
/*
* Do not stop the tick, if we are only one off
* or if the cpu is required for rcu
if ((long)delta_jiffies >= 1) {
/*
- * calculate the expiry time for the next timer wheel
- * timer
- */
- expires = ktime_add_ns(last_update, tick_period.tv64 *
- delta_jiffies);
-
- /*
* If this cpu is the one which updates jiffies, then
* give up the assignment and let it be taken by the
* cpu which runs the tick timer next, which might be
* this cpu as well. If we don't drop this here the
* jiffies might be stale and do_timer() never
- * invoked.
+ * invoked. Keep track of the fact that it was the one
+ * which had the do_timer() duty last. If this cpu is
+ * the one which had the do_timer() duty last, we
+ * limit the sleep time to the timekeeping
+ * max_deferement value which we retrieved
+ * above. Otherwise we can sleep as long as we want.
*/
- if (cpu == tick_do_timer_cpu)
+ if (cpu == tick_do_timer_cpu) {
tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+ ts->do_timer_last = 1;
+ } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
+ time_delta = KTIME_MAX;
+ ts->do_timer_last = 0;
+ } else if (!ts->do_timer_last) {
+ time_delta = KTIME_MAX;
+ }
+
+ /*
+ * calculate the expiry time for the next timer wheel
+ * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
+ * that there is no timer pending or at least extremely
+ * far into the future (12 days for HZ=1000). In this
+ * case we set the expiry to the end of time.
+ */
+ if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
+ /*
+ * Calculate the time delta for the next timer event.
+ * If the time delta exceeds the maximum time delta
+ * permitted by the current clocksource then adjust
+ * the time delta accordingly to ensure the
+ * clocksource does not wrap.
+ */
+ time_delta = min_t(u64, time_delta,
+ tick_period.tv64 * delta_jiffies);
+ }
+
+ if (time_delta < KTIME_MAX)
+ expires = ktime_add_ns(last_update, time_delta);
+ else
+ expires.tv64 = KTIME_MAX;
if (delta_jiffies > 1)
- cpu_set(cpu, nohz_cpu_mask);
+ cpumask_set_cpu(cpu, nohz_cpu_mask);
/* Skip reprogram of event if its not changed */
if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
/*
* sched tick not stopped!
*/
- cpu_clear(cpu, nohz_cpu_mask);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
goto out;
}
ts->idle_sleeps++;
+ /* Mark expires */
+ ts->idle_expires = expires;
+
/*
- * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that
- * there is no timer pending or at least extremly far
- * into the future (12 days for HZ=1000). In this case
- * we simply stop the tick timer:
+ * If the expiration time == KTIME_MAX, then
+ * in this case we simply stop the tick timer.
*/
- if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
- ts->idle_expires.tv64 = KTIME_MAX;
+ if (unlikely(expires.tv64 == KTIME_MAX)) {
if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
hrtimer_cancel(&ts->sched_timer);
goto out;
}
- /* Mark expiries */
- ts->idle_expires = expires;
-
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
hrtimer_start(&ts->sched_timer, expires,
- HRTIMER_MODE_ABS);
+ HRTIMER_MODE_ABS_PINNED);
/* Check, if the timer was already in the past */
if (hrtimer_active(&ts->sched_timer))
goto out;
* softirq.
*/
tick_do_update_jiffies64(ktime_get());
- cpu_clear(cpu, nohz_cpu_mask);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
}
raise_softirq_irqoff(TIMER_SOFTIRQ);
out:
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
hrtimer_start_expires(&ts->sched_timer,
- HRTIMER_MODE_ABS);
+ HRTIMER_MODE_ABS_PINNED);
/* Check, if the timer was already in the past */
if (hrtimer_active(&ts->sched_timer))
break;
ktime_t now;
local_irq_disable();
- tick_nohz_stop_idle(cpu);
+ if (ts->idle_active || (ts->inidle && ts->tick_stopped))
+ now = ktime_get();
+
+ if (ts->idle_active)
+ tick_nohz_stop_idle(cpu, now);
if (!ts->inidle || !ts->tick_stopped) {
ts->inidle = 0;
/* Update jiffies first */
select_nohz_load_balancer(0);
- now = ktime_get();
tick_do_update_jiffies64(now);
- cpu_clear(cpu, nohz_cpu_mask);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
/*
* timer and do not touch the other magic bits which need to be done
* when idle is left.
*/
-static void tick_nohz_kick_tick(int cpu)
+static void tick_nohz_kick_tick(int cpu, ktime_t now)
{
#if 0
/* Switch back to 2.6.27 behaviour */
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
- ktime_t delta, now;
-
- if (!ts->tick_stopped)
- return;
+ ktime_t delta;
/*
* Do not touch the tick device, when the next expiry is either
* already reached or less/equal than the tick period.
*/
- now = ktime_get();
delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
if (delta.tv64 <= tick_period.tv64)
return;
#endif
}
+static inline void tick_check_nohz(int cpu)
+{
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t now;
+
+ if (!ts->idle_active && !ts->tick_stopped)
+ return;
+ now = ktime_get();
+ if (ts->idle_active)
+ tick_nohz_stop_idle(cpu, now);
+ if (ts->tick_stopped) {
+ tick_nohz_update_jiffies(now);
+ tick_nohz_kick_tick(cpu, now);
+ }
+}
+
#else
static inline void tick_nohz_switch_to_nohz(void) { }
+static inline void tick_check_nohz(int cpu) { }
#endif /* NO_HZ */
void tick_check_idle(int cpu)
{
tick_check_oneshot_broadcast(cpu);
-#ifdef CONFIG_NO_HZ
- tick_nohz_stop_idle(cpu);
- tick_nohz_update_jiffies();
- tick_nohz_kick_tick(cpu);
-#endif
+ tick_check_nohz(cpu);
}
/*
for (;;) {
hrtimer_forward(&ts->sched_timer, now, tick_period);
- hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS);
+ hrtimer_start_expires(&ts->sched_timer,
+ HRTIMER_MODE_ABS_PINNED);
/* Check, if the timer was already in the past */
if (hrtimer_active(&ts->sched_timer))
break;
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff