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-rw-r--r--kernel/time/tick-sched.c296
1 files changed, 280 insertions, 16 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 225f8bf1909..bc67d4245e1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -21,11 +21,15 @@
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/irq_work.h>
+#include <linux/posix-timers.h>
+#include <linux/perf_event.h>
#include <asm/irq_regs.h>
#include "tick-internal.h"
+#include <trace/events/timer.h>
+
/*
* Per cpu nohz control structure
*/
@@ -104,7 +108,7 @@ static void tick_sched_do_timer(ktime_t now)
{
int cpu = smp_processor_id();
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* Check if the do_timer duty was dropped. We don't care about
* concurrency: This happens only when the cpu in charge went
@@ -112,7 +116,8 @@ static void tick_sched_do_timer(ktime_t now)
* this duty, then the jiffies update is still serialized by
* jiffies_lock.
*/
- if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
+ if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+ && !tick_nohz_full_cpu(cpu))
tick_do_timer_cpu = cpu;
#endif
@@ -123,7 +128,7 @@ static void tick_sched_do_timer(ktime_t now)
static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
{
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* When we are idle and the tick is stopped, we have to touch
* the watchdog as we might not schedule for a really long
@@ -142,10 +147,226 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
profile_tick(CPU_PROFILING);
}
+#ifdef CONFIG_NO_HZ_FULL
+static cpumask_var_t nohz_full_mask;
+bool have_nohz_full_mask;
+
+static bool can_stop_full_tick(void)
+{
+ WARN_ON_ONCE(!irqs_disabled());
+
+ if (!sched_can_stop_tick()) {
+ trace_tick_stop(0, "more than 1 task in runqueue\n");
+ return false;
+ }
+
+ if (!posix_cpu_timers_can_stop_tick(current)) {
+ trace_tick_stop(0, "posix timers running\n");
+ return false;
+ }
+
+ if (!perf_event_can_stop_tick()) {
+ trace_tick_stop(0, "perf events running\n");
+ return false;
+ }
+
+ /* sched_clock_tick() needs us? */
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+ /*
+ * TODO: kick full dynticks CPUs when
+ * sched_clock_stable is set.
+ */
+ if (!sched_clock_stable) {
+ trace_tick_stop(0, "unstable sched clock\n");
+ return false;
+ }
+#endif
+
+ 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 = &__get_cpu_var(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();
+}
+
+static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
+ .func = nohz_full_kick_work_func,
+};
+
+/*
+ * Kick the current CPU if it's full dynticks in order to force it to
+ * re-evaluate its dependency on the tick and restart it if necessary.
+ */
+void tick_nohz_full_kick(void)
+{
+ if (tick_nohz_full_cpu(smp_processor_id()))
+ irq_work_queue(&__get_cpu_var(nohz_full_kick_work));
+}
+
+static void nohz_full_kick_ipi(void *info)
+{
+ tick_nohz_full_check();
+}
+
+/*
+ * Kick all full dynticks CPUs in order to force these to re-evaluate
+ * their dependency on the tick and restart it if necessary.
+ */
+void tick_nohz_full_kick_all(void)
+{
+ if (!have_nohz_full_mask)
+ return;
+
+ preempt_disable();
+ smp_call_function_many(nohz_full_mask,
+ nohz_full_kick_ipi, NULL, false);
+ preempt_enable();
+}
+
+/*
+ * Re-evaluate the need for the tick as we switch the current task.
+ * 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)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+
+ if (!tick_nohz_full_cpu(smp_processor_id()))
+ goto out;
+
+ if (tick_nohz_tick_stopped() && !can_stop_full_tick())
+ tick_nohz_full_kick();
+
+out:
+ local_irq_restore(flags);
+}
+
+int tick_nohz_full_cpu(int cpu)
+{
+ if (!have_nohz_full_mask)
+ return 0;
+
+ return cpumask_test_cpu(cpu, nohz_full_mask);
+}
+
+/* Parse the boot-time nohz CPU list from the kernel parameters. */
+static int __init tick_nohz_full_setup(char *str)
+{
+ int cpu;
+
+ alloc_bootmem_cpumask_var(&nohz_full_mask);
+ if (cpulist_parse(str, nohz_full_mask) < 0) {
+ pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
+ return 1;
+ }
+
+ cpu = smp_processor_id();
+ if (cpumask_test_cpu(cpu, nohz_full_mask)) {
+ pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu);
+ cpumask_clear_cpu(cpu, nohz_full_mask);
+ }
+ have_nohz_full_mask = true;
+
+ return 1;
+}
+__setup("nohz_full=", tick_nohz_full_setup);
+
+static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
+ 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.
+ */
+ if (have_nohz_full_mask && tick_do_timer_cpu == cpu)
+ return -EINVAL;
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+/*
+ * Worst case string length in chunks of CPU range seems 2 steps
+ * separations: 0,2,4,6,...
+ * This is NR_CPUS + sizeof('\0')
+ */
+static char __initdata nohz_full_buf[NR_CPUS + 1];
+
+static int tick_nohz_init_all(void)
+{
+ int err = -1;
+
+#ifdef CONFIG_NO_HZ_FULL_ALL
+ if (!alloc_cpumask_var(&nohz_full_mask, GFP_KERNEL)) {
+ pr_err("NO_HZ: Can't allocate full dynticks cpumask\n");
+ return err;
+ }
+ err = 0;
+ cpumask_setall(nohz_full_mask);
+ cpumask_clear_cpu(smp_processor_id(), nohz_full_mask);
+ have_nohz_full_mask = true;
+#endif
+ return err;
+}
+
+void __init tick_nohz_init(void)
+{
+ int cpu;
+
+ if (!have_nohz_full_mask) {
+ if (tick_nohz_init_all() < 0)
+ return;
+ }
+
+ cpu_notifier(tick_nohz_cpu_down_callback, 0);
+
+ /* Make sure full dynticks CPU are also RCU nocbs */
+ for_each_cpu(cpu, nohz_full_mask) {
+ if (!rcu_is_nocb_cpu(cpu)) {
+ pr_warning("NO_HZ: CPU %d is not RCU nocb: "
+ "cleared from nohz_full range", cpu);
+ cpumask_clear_cpu(cpu, nohz_full_mask);
+ }
+ }
+
+ cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask);
+ pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
+}
+#else
+#define have_nohz_full_mask (0)
+#endif
+
/*
* NOHZ - aka dynamic tick functionality
*/
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* NO HZ enabled ?
*/
@@ -345,11 +566,12 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
delta_jiffies = rcu_delta_jiffies;
}
}
+
/*
- * Do not stop the tick, if we are only one off
- * or if the cpu is required for rcu
+ * Do not stop the tick, if we are only one off (or less)
+ * or if the cpu is required for RCU:
*/
- if (!ts->tick_stopped && delta_jiffies == 1)
+ if (!ts->tick_stopped && delta_jiffies <= 1)
goto out;
/* Schedule the tick, if we are at least one jiffie off */
@@ -378,6 +600,13 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
time_delta = KTIME_MAX;
}
+#ifdef CONFIG_NO_HZ_FULL
+ if (!ts->inidle) {
+ time_delta = min(time_delta,
+ scheduler_tick_max_deferment());
+ }
+#endif
+
/*
* calculate the expiry time for the next timer wheel
* timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
@@ -421,6 +650,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
ts->tick_stopped = 1;
+ trace_tick_stop(1, " ");
}
/*
@@ -457,6 +687,24 @@ out:
return ret;
}
+static void tick_nohz_full_stop_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))
+ 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);
+#endif
+}
+
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
{
/*
@@ -489,6 +737,21 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
return false;
}
+ if (have_nohz_full_mask) {
+ /*
+ * Keep the tick alive to guarantee timekeeping progression
+ * if there are full dynticks CPUs around
+ */
+ if (tick_do_timer_cpu == cpu)
+ return false;
+ /*
+ * Boot safety: make sure the timekeeping duty has been
+ * assigned before entering dyntick-idle mode,
+ */
+ if (tick_do_timer_cpu == TICK_DO_TIMER_NONE)
+ return false;
+ }
+
return true;
}
@@ -568,12 +831,13 @@ void tick_nohz_irq_exit(void)
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
- if (!ts->inidle)
- return;
-
- /* Cancel the timer because CPU already waken up from the C-states*/
- menu_hrtimer_cancel();
- __tick_nohz_idle_enter(ts);
+ if (ts->inidle) {
+ /* Cancel the timer because CPU already waken up from the C-states*/
+ menu_hrtimer_cancel();
+ __tick_nohz_idle_enter(ts);
+ } else {
+ tick_nohz_full_stop_tick(ts);
+ }
}
/**
@@ -802,7 +1066,7 @@ static inline void tick_check_nohz(int cpu)
static inline void tick_nohz_switch_to_nohz(void) { }
static inline void tick_check_nohz(int cpu) { }
-#endif /* NO_HZ */
+#endif /* CONFIG_NO_HZ_COMMON */
/*
* Called from irq_enter to notify about the possible interruption of idle()
@@ -887,14 +1151,14 @@ void tick_setup_sched_timer(void)
now = ktime_get();
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
if (tick_nohz_enabled)
ts->nohz_mode = NOHZ_MODE_HIGHRES;
#endif
}
#endif /* HIGH_RES_TIMERS */
-#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
+#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
void tick_cancel_sched_timer(int cpu)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);