return true;
}
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now);
-
-/*
- * Re-evaluate the need for the tick on the current CPU
- * and restart it if necessary.
- */
-void __tick_nohz_full_check(void)
-{
- struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
-
- if (tick_nohz_full_cpu(smp_processor_id())) {
- if (ts->tick_stopped && !is_idle_task(current)) {
- if (!can_stop_full_tick())
- tick_nohz_restart_sched_tick(ts, ktime_get());
- }
- }
-}
-
static void nohz_full_kick_work_func(struct irq_work *work)
{
- __tick_nohz_full_check();
+ /* Empty, the tick restart happens on tick_nohz_irq_exit() */
}
static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
static void nohz_full_kick_ipi(void *info)
{
- __tick_nohz_full_check();
+ /* Empty, the tick restart happens on tick_nohz_irq_exit() */
}
/*
* It might need the tick due to per task/process properties:
* perf events, posix cpu timers, ...
*/
-void __tick_nohz_task_switch(struct task_struct *tsk)
+void __tick_nohz_task_switch(void)
{
unsigned long flags;
__setup("nohz_full=", tick_nohz_full_setup);
static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
- unsigned long action,
- void *hcpu)
+ unsigned long action,
+ void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
/*
- * If we handle the timekeeping duty for full dynticks CPUs,
- * we can't safely shutdown that CPU.
+ * The boot CPU handles housekeeping duty (unbound timers,
+ * workqueues, timekeeping, ...) on behalf of full dynticks
+ * CPUs. It must remain online when nohz full is enabled.
*/
if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
return NOTIFY_BAD;
cpu_notifier(tick_nohz_cpu_down_callback, 0);
pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
cpumask_pr_args(tick_nohz_full_mask));
+
+ /*
+ * We need at least one CPU to handle housekeeping work such
+ * as timekeeping, unbound timers, workqueues, ...
+ */
+ WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
}
#endif
* NO HZ enabled ?
*/
static int tick_nohz_enabled __read_mostly = 1;
-int tick_nohz_active __read_mostly;
+unsigned long tick_nohz_active __read_mostly;
/*
* Enable / Disable tickless mode
*/
static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
{
- hrtimer_cancel(&ts->sched_timer);
- hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
+ hrtimer_cancel(&ts->sched_timer);
+ hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
- /* Forward the time to expire in the future */
- hrtimer_forward(&ts->sched_timer, now, tick_period);
+ /* Forward the time to expire in the future */
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
- hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
- else
- tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
+ else
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
}
static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
ktime_t now, int cpu)
{
- unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
- ktime_t last_update, expires, ret = { .tv64 = 0 };
- unsigned long rcu_delta_jiffies;
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
- u64 time_delta;
-
- time_delta = timekeeping_max_deferment();
+ u64 basemono, next_tick, next_tmr, next_rcu, delta, expires;
+ unsigned long seq, basejiff;
+ ktime_t tick;
/* Read jiffies and the time when jiffies were updated last */
do {
seq = read_seqcount_begin(&jiffies_seq);
- last_update = last_jiffies_update;
- last_jiffies = jiffies;
+ basemono = last_jiffies_update.tv64;
+ basejiff = jiffies;
} while (read_seqcount_retry(&jiffies_seq, seq));
+ ts->last_jiffies = basejiff;
- if (rcu_needs_cpu(&rcu_delta_jiffies) ||
+ if (rcu_needs_cpu(basemono, &next_rcu) ||
arch_needs_cpu() || irq_work_needs_cpu()) {
- next_jiffies = last_jiffies + 1;
- delta_jiffies = 1;
+ next_tick = basemono + TICK_NSEC;
} else {
- /* Get the next timer wheel timer */
- next_jiffies = get_next_timer_interrupt(last_jiffies);
- delta_jiffies = next_jiffies - last_jiffies;
- if (rcu_delta_jiffies < delta_jiffies) {
- next_jiffies = last_jiffies + rcu_delta_jiffies;
- delta_jiffies = rcu_delta_jiffies;
- }
+ /*
+ * Get the next pending timer. If high resolution
+ * timers are enabled this only takes the timer wheel
+ * timers into account. If high resolution timers are
+ * disabled this also looks at the next expiring
+ * hrtimer.
+ */
+ next_tmr = get_next_timer_interrupt(basejiff, basemono);
+ ts->next_timer = next_tmr;
+ /* Take the next rcu event into account */
+ next_tick = next_rcu < next_tmr ? next_rcu : next_tmr;
}
/*
- * Do not stop the tick, if we are only one off (or less)
- * or if the cpu is required for RCU:
+ * If the tick is due in the next period, keep it ticking or
+ * restart it proper.
*/
- if (!ts->tick_stopped && delta_jiffies <= 1)
- goto out;
-
- /* Schedule the tick, if we are at least one jiffie off */
- if ((long)delta_jiffies >= 1) {
-
- /*
- * 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. 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) {
- 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;
+ delta = next_tick - basemono;
+ if (delta <= (u64)TICK_NSEC) {
+ tick.tv64 = 0;
+ if (!ts->tick_stopped)
+ goto out;
+ if (delta == 0) {
+ /* Tick is stopped, but required now. Enforce it */
+ tick_nohz_restart(ts, now);
+ goto out;
}
+ }
+
+ /*
+ * 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. 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.
+ * Otherwise we can sleep as long as we want.
+ */
+ delta = timekeeping_max_deferment();
+ 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) {
+ delta = KTIME_MAX;
+ ts->do_timer_last = 0;
+ } else if (!ts->do_timer_last) {
+ delta = KTIME_MAX;
+ }
#ifdef CONFIG_NO_HZ_FULL
- if (!ts->inidle) {
- time_delta = min(time_delta,
- scheduler_tick_max_deferment());
- }
+ /* Limit the tick delta to the maximum scheduler deferment */
+ if (!ts->inidle)
+ delta = min(delta, scheduler_tick_max_deferment());
#endif
- /*
- * 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;
-
- /* Skip reprogram of event if its not changed */
- if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
- goto out;
+ /* Calculate the next expiry time */
+ if (delta < (KTIME_MAX - basemono))
+ expires = basemono + delta;
+ else
+ expires = KTIME_MAX;
- ret = expires;
+ expires = min_t(u64, expires, next_tick);
+ tick.tv64 = expires;
- /*
- * nohz_stop_sched_tick can be called several times before
- * the nohz_restart_sched_tick is called. This happens when
- * interrupts arrive which do not cause a reschedule. In the
- * first call we save the current tick time, so we can restart
- * the scheduler tick in nohz_restart_sched_tick.
- */
- if (!ts->tick_stopped) {
- nohz_balance_enter_idle(cpu);
- calc_load_enter_idle();
-
- ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
- ts->tick_stopped = 1;
- trace_tick_stop(1, " ");
- }
+ /* Skip reprogram of event if its not changed */
+ if (ts->tick_stopped && (expires == dev->next_event.tv64))
+ goto out;
- /*
- * If the expiration time == KTIME_MAX, then
- * in this case we simply stop the tick timer.
- */
- if (unlikely(expires.tv64 == KTIME_MAX)) {
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
- hrtimer_cancel(&ts->sched_timer);
- goto out;
- }
+ /*
+ * nohz_stop_sched_tick can be called several times before
+ * the nohz_restart_sched_tick is called. This happens when
+ * interrupts arrive which do not cause a reschedule. In the
+ * first call we save the current tick time, so we can restart
+ * the scheduler tick in nohz_restart_sched_tick.
+ */
+ if (!ts->tick_stopped) {
+ nohz_balance_enter_idle(cpu);
+ calc_load_enter_idle();
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
- hrtimer_start(&ts->sched_timer, expires,
- HRTIMER_MODE_ABS_PINNED);
- else
- tick_program_event(expires, 1);
- } else {
- /* Tick is stopped, but required now. Enforce it */
- tick_nohz_restart(ts, now);
+ ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
+ ts->tick_stopped = 1;
+ trace_tick_stop(1, " ");
+ }
+ /*
+ * If the expiration time == KTIME_MAX, then we simply stop
+ * the tick timer.
+ */
+ if (unlikely(expires == KTIME_MAX)) {
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_cancel(&ts->sched_timer);
+ goto out;
}
+
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_start(&ts->sched_timer, tick, HRTIMER_MODE_ABS_PINNED);
+ else
+ tick_program_event(tick, 1);
out:
- ts->next_jiffies = next_jiffies;
- ts->last_jiffies = last_jiffies;
+ /* Update the estimated sleep length */
ts->sleep_length = ktime_sub(dev->next_event, now);
+ return tick;
+}
- return ret;
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
+{
+ /* Update jiffies first */
+ tick_do_update_jiffies64(now);
+ update_cpu_load_nohz();
+
+ calc_load_exit_idle();
+ touch_softlockup_watchdog();
+ /*
+ * Cancel the scheduled timer and restore the tick
+ */
+ ts->tick_stopped = 0;
+ ts->idle_exittime = now;
+
+ tick_nohz_restart(ts, now);
}
-static void tick_nohz_full_stop_tick(struct tick_sched *ts)
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
{
#ifdef CONFIG_NO_HZ_FULL
int cpu = smp_processor_id();
- if (!tick_nohz_full_cpu(cpu) || is_idle_task(current))
+ if (!tick_nohz_full_cpu(cpu))
return;
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
return;
- if (!can_stop_full_tick())
- return;
-
- tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+ if (can_stop_full_tick())
+ tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
+ else if (ts->tick_stopped)
+ tick_nohz_restart_sched_tick(ts, ktime_get());
#endif
}
if (ts->inidle)
__tick_nohz_idle_enter(ts);
else
- tick_nohz_full_stop_tick(ts);
+ tick_nohz_full_update_tick(ts);
}
/**
return ts->sleep_length;
}
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
-{
- /* Update jiffies first */
- tick_do_update_jiffies64(now);
- update_cpu_load_nohz();
-
- calc_load_exit_idle();
- touch_softlockup_watchdog();
- /*
- * Cancel the scheduled timer and restore the tick
- */
- ts->tick_stopped = 0;
- ts->idle_exittime = now;
-
- tick_nohz_restart(ts, now);
-}
-
static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
{
#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
local_irq_enable();
}
-static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
-{
- hrtimer_forward(&ts->sched_timer, now, tick_period);
- return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
-}
-
/*
* The nohz low res interrupt handler
*/
if (unlikely(ts->tick_stopped))
return;
- while (tick_nohz_reprogram(ts, now)) {
- now = ktime_get();
- tick_do_update_jiffies64(now);
- }
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+}
+
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
+{
+ if (!tick_nohz_enabled)
+ return;
+ ts->nohz_mode = mode;
+ /* One update is enough */
+ if (!test_and_set_bit(0, &tick_nohz_active))
+ timers_update_migration(true);
}
/**
if (!tick_nohz_enabled)
return;
- local_irq_disable();
- if (tick_switch_to_oneshot(tick_nohz_handler)) {
- local_irq_enable();
+ if (tick_switch_to_oneshot(tick_nohz_handler))
return;
- }
- tick_nohz_active = 1;
- ts->nohz_mode = NOHZ_MODE_LOWRES;
/*
* Recycle the hrtimer in ts, so we can share the
/* Get the next period */
next = tick_init_jiffy_update();
- for (;;) {
- hrtimer_set_expires(&ts->sched_timer, next);
- if (!tick_program_event(next, 0))
- break;
- next = ktime_add(next, tick_period);
- }
- local_irq_enable();
+ hrtimer_set_expires(&ts->sched_timer, next);
+ hrtimer_forward_now(&ts->sched_timer, tick_period);
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+ tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
}
/*
static inline void tick_nohz_switch_to_nohz(void) { }
static inline void tick_nohz_irq_enter(void) { }
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
#endif /* CONFIG_NO_HZ_COMMON */
hrtimer_add_expires_ns(&ts->sched_timer, offset);
}
- for (;;) {
- hrtimer_forward(&ts->sched_timer, now, tick_period);
- 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;
- now = ktime_get();
- }
-
-#ifdef CONFIG_NO_HZ_COMMON
- if (tick_nohz_enabled) {
- ts->nohz_mode = NOHZ_MODE_HIGHRES;
- tick_nohz_active = 1;
- }
-#endif
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
+ tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
}
#endif /* HIGH_RES_TIMERS */
* Called cyclic from the hrtimer softirq (driven by the timer
* softirq) allow_nohz signals, that we can switch into low-res nohz
* mode, because high resolution timers are disabled (either compile
- * or runtime).
+ * or runtime). Called with interrupts disabled.
*/
int tick_check_oneshot_change(int allow_nohz)
{
Code Review / kvmfornfv.git / blobdiff