From: Ingo Molnar <[email protected]>
dynticks core code.
Add idling-stats to the cpu base (to be used to optimize power
management decisions), add the scheduler tick and its stop/restart
functions, and the jiffies-update function to be called when an irq
context hits the idle context.
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
--
include/linux/hrtimer.h | 28 +++++++
kernel/hrtimer.c | 185 ++++++++++++++++++++++++++++++++++++++++++++++--
kernel/softirq.c | 11 ++
kernel/time/Kconfig | 8 ++
kernel/timer.c | 2
5 files changed, 226 insertions(+), 8 deletions(-)
Index: linux-2.6.18-mm2/include/linux/hrtimer.h
===================================================================
--- linux-2.6.18-mm2.orig/include/linux/hrtimer.h 2006-09-30 01:41:18.000000000 +0200
+++ linux-2.6.18-mm2/include/linux/hrtimer.h 2006-09-30 01:41:18.000000000 +0200
@@ -142,6 +142,14 @@ struct hrtimer_cpu_base {
struct hrtimer sched_timer;
struct pt_regs *sched_regs;
unsigned long events;
+#ifdef CONFIG_NO_HZ
+ ktime_t idle_tick;
+ int tick_stopped;
+ unsigned long idle_jiffies;
+ unsigned long idle_calls;
+ unsigned long idle_sleeps;
+ unsigned long idle_sleeptime;
+#endif
#endif
};
@@ -200,7 +208,7 @@ extern int hrtimer_try_to_cancel(struct
extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);
-#ifdef CONFIG_NO_IDLE_HZ
+#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
extern ktime_t hrtimer_get_next_event(void);
#endif
@@ -229,6 +237,24 @@ extern void hrtimer_run_queues(void);
/* Resume notification */
void hrtimer_notify_resume(void);
+#ifdef CONFIG_NO_HZ
+extern void hrtimer_trigger_next_hz_tick(struct tvec_t_base_s *base);
+extern int hrtimer_stop_sched_tick(void);
+extern void hrtimer_restart_sched_tick(void);
+extern void update_jiffies(void);
+struct seq_file;
+extern void show_no_hz_stats(struct seq_file *p);
+#else
+# define hrtimer_trigger_next_hz_tick(base) do { } while (0)
+static inline int hrtimer_stop_sched_tick(void)
+{
+ return 0;
+}
+# define hrtimer_restart_sched_tick() do { } while (0)
+# define update_jiffies() do { } while (0)
+# define show_no_hz_stats(p) do { } while (0)
+#endif
+
/* Bootup initialization: */
extern void __init hrtimers_init(void);
Index: linux-2.6.18-mm2/kernel/hrtimer.c
===================================================================
--- linux-2.6.18-mm2.orig/kernel/hrtimer.c 2006-09-30 01:41:18.000000000 +0200
+++ linux-2.6.18-mm2/kernel/hrtimer.c 2006-09-30 01:41:18.000000000 +0200
@@ -437,7 +437,6 @@ static void update_jiffies64(ktime_t now
delta = ktime_sub(now, last_jiffies_update);
if (delta.tv64 >= nsec_per_hz.tv64) {
-
unsigned long orun = 1;
delta = ktime_sub(delta, nsec_per_hz);
@@ -451,7 +450,6 @@ static void update_jiffies64(ktime_t now
last_jiffies_update = ktime_add_ns(last_jiffies_update,
incr * orun);
- jiffies_64 += orun;
orun++;
}
do_timer(orun);
@@ -459,28 +457,201 @@ static void update_jiffies64(ktime_t now
write_sequnlock(&xtime_lock);
}
+#ifdef CONFIG_NO_HZ
+/*
+ * Called from interrupt entry when then CPU was idle
+ */
+void update_jiffies(void)
+{
+ unsigned long flags;
+ ktime_t now;
+
+ if (unlikely(!hrtimer_hres_active))
+ return;
+
+ now = ktime_get();
+
+ local_irq_save(flags);
+ update_jiffies64(now);
+ local_irq_restore(flags);
+}
+
+/*
+ * Called from the idle thread so careful!
+ */
+int hrtimer_stop_sched_tick(void)
+{
+ int cpu = smp_processor_id();
+ struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
+ unsigned long seq, last_jiffies, next_jiffies;
+ ktime_t last_update, expires;
+ unsigned long delta_jiffies;
+ unsigned long flags;
+
+ if (unlikely(!hrtimer_hres_active))
+ return 0;
+
+ local_irq_save(flags);
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ last_update = last_jiffies_update;
+ last_jiffies = jiffies;
+ } while (read_seqretry(&xtime_lock, seq));
+
+ next_jiffies = get_next_timer_interrupt(last_jiffies);
+ delta_jiffies = next_jiffies - last_jiffies;
+
+ cpu_base->idle_calls++;
+
+ if ((long)delta_jiffies >= 1) {
+ /*
+ * Save the current tick time, so we can restart the
+ * scheduler tick when we get woken up before the next
+ * wheel timer expires
+ */
+ cpu_base->idle_tick = cpu_base->sched_timer.expires;
+ expires = ktime_add_ns(last_update,
+ nsec_per_hz.tv64 * delta_jiffies);
+ hrtimer_start(&cpu_base->sched_timer, expires, HRTIMER_ABS);
+ cpu_base->idle_sleeps++;
+ cpu_base->idle_jiffies = last_jiffies;
+ cpu_base->tick_stopped = 1;
+ } else {
+ /* Keep the timer alive */
+ if ((long) delta_jiffies < 0)
+ raise_softirq(TIMER_SOFTIRQ);
+ }
+
+ if (local_softirq_pending()) {
+ inc_preempt_count();
+ do_softirq();
+ dec_preempt_count();
+ }
+
+ WARN_ON(!idle_cpu(cpu));
+ /*
+ * RCU normally depends on the timer IRQ kicking completion
+ * in every tick. We have to do this here now:
+ */
+ if (rcu_pending(cpu)) {
+ /*
+ * We are in quiescent state, so advance callbacks:
+ */
+ rcu_advance_callbacks(cpu, 1);
+ local_irq_enable();
+ local_bh_disable();
+ rcu_process_callbacks(0);
+ local_bh_enable();
+ }
+
+ local_irq_restore(flags);
+
+ return need_resched();
+}
+
+void hrtimer_restart_sched_tick(void)
+{
+ struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
+ unsigned long flags;
+ ktime_t now;
+
+ if (!hrtimer_hres_active || !cpu_base->tick_stopped)
+ return;
+
+ /* Update jiffies first */
+ now = ktime_get();
+
+ local_irq_save(flags);
+ update_jiffies64(now);
+
+ /*
+ * Update process times would randomly account the time we slept to
+ * whatever the context of the next sched tick is. Enforce that this
+ * is accounted to idle !
+ */
+ add_preempt_count(HARDIRQ_OFFSET);
+ update_process_times(0);
+ sub_preempt_count(HARDIRQ_OFFSET);
+
+ cpu_base->idle_sleeptime += jiffies - cpu_base->idle_jiffies;
+
+ cpu_base->tick_stopped = 0;
+ hrtimer_cancel(&cpu_base->sched_timer);
+ cpu_base->sched_timer.expires = cpu_base->idle_tick;
+
+ while (1) {
+ hrtimer_forward(&cpu_base->sched_timer, now, nsec_per_hz);
+ hrtimer_start(&cpu_base->sched_timer,
+ cpu_base->sched_timer.expires, HRTIMER_ABS);
+ if (hrtimer_active(&cpu_base->sched_timer))
+ break;
+ /* We missed an update */
+ update_jiffies64(now);
+ now = ktime_get();
+ }
+ local_irq_restore(flags);
+}
+
+void show_no_hz_stats(struct seq_file *p)
+{
+ int cpu;
+ unsigned long calls = 0, sleeps = 0, time = 0, events = 0;
+
+ for_each_online_cpu(cpu) {
+ struct hrtimer_cpu_base *base = &per_cpu(hrtimer_bases, cpu);
+
+ calls += base->idle_calls;
+ sleeps += base->idle_sleeps;
+ time += base->idle_sleeptime;
+ events += base->events;
+
+ seq_printf(p, "nohz cpu%d I:%lu S:%lu T:%lu A:%lu E: %lu\n",
+ cpu, base->idle_calls, base->idle_sleeps,
+ base->idle_sleeptime, base->idle_sleeps ?
+ base->idle_sleeptime / sleeps : 0, base->events);
+ }
+#ifdef CONFIG_SMP
+ seq_printf(p, "nohz total I:%lu S:%lu T:%lu A:%lu E:%lu\n",
+ calls, sleeps, time, sleeps ? time / sleeps : 0, events);
+#endif
+}
+
+#endif
+
+
/*
* We rearm the timer until we get disabled by the idle code
+ * Called with interrupts disabled.
*/
static int hrtimer_sched_tick(struct hrtimer *timer)
{
- unsigned long flags;
struct hrtimer_cpu_base *cpu_base =
container_of(timer, struct hrtimer_cpu_base, sched_timer);
- local_irq_save(flags);
/*
* Do not call, when we are not in irq context and have
* no valid regs pointer
*/
if (cpu_base->sched_regs) {
+ /*
+ * update_process_times() might take tasklist_lock, hence
+ * drop the base lock. sched-tick hrtimers are per-CPU and
+ * never accessible by userspace APIs, so this is safe to do.
+ */
+ spin_unlock(&cpu_base->lock);
update_process_times(user_mode(cpu_base->sched_regs));
profile_tick(CPU_PROFILING, cpu_base->sched_regs);
+ spin_lock(&cpu_base->lock);
}
hrtimer_forward(timer, hrtimer_cb_get_time(timer), nsec_per_hz);
- local_irq_restore(flags);
+#ifdef CONFIG_NO_HZ
+ /* Do not restart, when we are in the idle loop */
+ if (cpu_base->tick_stopped)
+ return HRTIMER_NORESTART;
+#endif
return HRTIMER_RESTART;
}
@@ -908,7 +1079,7 @@ ktime_t hrtimer_get_remaining(const stru
}
EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
-#ifdef CONFIG_NO_IDLE_HZ
+#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
/**
* hrtimer_get_next_event - get the time until next expiry event
*
@@ -923,12 +1094,14 @@ ktime_t hrtimer_get_next_event(void)
unsigned long flags;
int i;
+#ifndef CONFIG_NO_HZ
/*
* In high-res mode we dont need to get the next high-res
* event on a tickless system:
*/
if (hrtimer_hres_active)
return mindelta;
+#endif
spin_lock_irqsave(&cpu_base->lock, flags);
Index: linux-2.6.18-mm2/kernel/softirq.c
===================================================================
--- linux-2.6.18-mm2.orig/kernel/softirq.c 2006-09-30 01:41:16.000000000 +0200
+++ linux-2.6.18-mm2/kernel/softirq.c 2006-09-30 01:41:18.000000000 +0200
@@ -284,6 +284,11 @@ extern void irq_enter(void)
account_system_vtime(current);
add_preempt_count(HARDIRQ_OFFSET);
trace_hardirq_enter();
+
+#ifdef CONFIG_NO_HZ
+ if (idle_cpu(smp_processor_id()))
+ update_jiffies();
+#endif
}
/*
@@ -296,6 +301,12 @@ void irq_exit(void)
sub_preempt_count(IRQ_EXIT_OFFSET);
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
+
+#ifdef CONFIG_NO_HZ
+ /* Make sure that timer wheel updates are propagated */
+ if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
+ hrtimer_stop_sched_tick();
+#endif
preempt_enable_no_resched();
}
Index: linux-2.6.18-mm2/kernel/time/Kconfig
===================================================================
--- linux-2.6.18-mm2.orig/kernel/time/Kconfig 2006-09-30 01:41:18.000000000 +0200
+++ linux-2.6.18-mm2/kernel/time/Kconfig 2006-09-30 01:41:18.000000000 +0200
@@ -20,3 +20,11 @@ config HIGH_RES_RESOLUTION
800 MHz processor about 10,000 (10 microseconds) is recommended as a
finest resolution. If you don't need that sort of resolution,
larger values may generate less overhead.
+
+config NO_HZ
+ bool "Tickless System (Dynamic Ticks)"
+ depends on GENERIC_TIME && HIGH_RES_TIMERS
+ help
+ This option enables a tickless system: timer interrupts will
+ only trigger on an as-needed basis both when the system is
+ busy and when the system is idle.
Index: linux-2.6.18-mm2/kernel/timer.c
===================================================================
--- linux-2.6.18-mm2.orig/kernel/timer.c 2006-09-30 01:41:18.000000000 +0200
+++ linux-2.6.18-mm2/kernel/timer.c 2006-09-30 01:41:18.000000000 +0200
@@ -462,7 +462,7 @@ static inline void __run_timers(tvec_bas
spin_unlock_irq(&base->lock);
}
-#ifdef CONFIG_NO_IDLE_HZ
+#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
/*
* Find out when the next timer event is due to happen. This
* is used on S/390 to stop all activity when a cpus is idle.
--
-
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