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authorLinus Torvalds <torvalds@linux-foundation.org>2013-05-05 13:23:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-05 13:23:27 -0700
commit534c97b0950b1967bca1c753aeaed32f5db40264 (patch)
tree9421d26e4f6d479d1bc32b036a731b065daab0fa /kernel
parent64049d1973c1735f543eb7a55653e291e108b0cb (diff)
parent265f22a975c1e4cc3a4d1f94a3ec53ffbb6f5b9f (diff)
downloadlinaro-lsk-534c97b0950b1967bca1c753aeaed32f5db40264.tar.gz
Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull 'full dynticks' support from Ingo Molnar: "This tree from Frederic Weisbecker adds a new, (exciting! :-) core kernel feature to the timer and scheduler subsystems: 'full dynticks', or CONFIG_NO_HZ_FULL=y. This feature extends the nohz variable-size timer tick feature from idle to busy CPUs (running at most one task) as well, potentially reducing the number of timer interrupts significantly. This feature got motivated by real-time folks and the -rt tree, but the general utility and motivation of full-dynticks runs wider than that: - HPC workloads get faster: CPUs running a single task should be able to utilize a maximum amount of CPU power. A periodic timer tick at HZ=1000 can cause a constant overhead of up to 1.0%. This feature removes that overhead - and speeds up the system by 0.5%-1.0% on typical distro configs even on modern systems. - Real-time workload latency reduction: CPUs running critical tasks should experience as little jitter as possible. The last remaining source of kernel-related jitter was the periodic timer tick. - A single task executing on a CPU is a pretty common situation, especially with an increasing number of cores/CPUs, so this feature helps desktop and mobile workloads as well. The cost of the feature is mainly related to increased timer reprogramming overhead when a CPU switches its tick period, and thus slightly longer to-idle and from-idle latency. Configuration-wise a third mode of operation is added to the existing two NOHZ kconfig modes: - CONFIG_HZ_PERIODIC: [formerly !CONFIG_NO_HZ], now explicitly named as a config option. This is the traditional Linux periodic tick design: there's a HZ tick going on all the time, regardless of whether a CPU is idle or not. - CONFIG_NO_HZ_IDLE: [formerly CONFIG_NO_HZ=y], this turns off the periodic tick when a CPU enters idle mode. - CONFIG_NO_HZ_FULL: this new mode, in addition to turning off the tick when a CPU is idle, also slows the tick down to 1 Hz (one timer interrupt per second) when only a single task is running on a CPU. The .config behavior is compatible: existing !CONFIG_NO_HZ and CONFIG_NO_HZ=y settings get translated to the new values, without the user having to configure anything. CONFIG_NO_HZ_FULL is turned off by default. This feature is based on a lot of infrastructure work that has been steadily going upstream in the last 2-3 cycles: related RCU support and non-periodic cputime support in particular is upstream already. This tree adds the final pieces and activates the feature. The pull request is marked RFC because: - it's marked 64-bit only at the moment - the 32-bit support patch is small but did not get ready in time. - it has a number of fresh commits that came in after the merge window. The overwhelming majority of commits are from before the merge window, but still some aspects of the tree are fresh and so I marked it RFC. - it's a pretty wide-reaching feature with lots of effects - and while the components have been in testing for some time, the full combination is still not very widely used. That it's default-off should reduce its regression abilities and obviously there are no known regressions with CONFIG_NO_HZ_FULL=y enabled either. - the feature is not completely idempotent: there is no 100% equivalent replacement for a periodic scheduler/timer tick. In particular there's ongoing work to map out and reduce its effects on scheduler load-balancing and statistics. This should not impact correctness though, there are no known regressions related to this feature at this point. - it's a pretty ambitious feature that with time will likely be enabled by most Linux distros, and we'd like you to make input on its design/implementation, if you dislike some aspect we missed. Without flaming us to crisp! :-) Future plans: - there's ongoing work to reduce 1Hz to 0Hz, to essentially shut off the periodic tick altogether when there's a single busy task on a CPU. We'd first like 1 Hz to be exposed more widely before we go for the 0 Hz target though. - once we reach 0 Hz we can remove the periodic tick assumption from nr_running>=2 as well, by essentially interrupting busy tasks only as frequently as the sched_latency constraints require us to do - once every 4-40 msecs, depending on nr_running. I am personally leaning towards biting the bullet and doing this in v3.10, like the -rt tree this effort has been going on for too long - but the final word is up to you as usual. More technical details can be found in Documentation/timers/NO_HZ.txt" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (39 commits) sched: Keep at least 1 tick per second for active dynticks tasks rcu: Fix full dynticks' dependency on wide RCU nocb mode nohz: Protect smp_processor_id() in tick_nohz_task_switch() nohz_full: Add documentation. cputime_nsecs: use math64.h for nsec resolution conversion helpers nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config nohz: Reduce overhead under high-freq idling patterns nohz: Remove full dynticks' superfluous dependency on RCU tree nohz: Fix unavailable tick_stop tracepoint in dynticks idle nohz: Add basic tracing nohz: Select wide RCU nocb for full dynticks nohz: Disable the tick when irq resume in full dynticks CPU nohz: Re-evaluate the tick for the new task after a context switch nohz: Prepare to stop the tick on irq exit nohz: Implement full dynticks kick nohz: Re-evaluate the tick from the scheduler IPI sched: New helper to prevent from stopping the tick in full dynticks sched: Kick full dynticks CPU that have more than one task enqueued. perf: New helper to prevent full dynticks CPUs from stopping tick perf: Kick full dynticks CPU if events rotation is needed ...
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c17
-rw-r--r--kernel/hrtimer.c4
-rw-r--r--kernel/posix-cpu-timers.c76
-rw-r--r--kernel/rcutree.c16
-rw-r--r--kernel/rcutree.h2
-rw-r--r--kernel/rcutree_plugin.h33
-rw-r--r--kernel/sched/core.c92
-rw-r--r--kernel/sched/fair.c10
-rw-r--r--kernel/sched/idle_task.c1
-rw-r--r--kernel/sched/sched.h25
-rw-r--r--kernel/softirq.c19
-rw-r--r--kernel/time/Kconfig80
-rw-r--r--kernel/time/tick-broadcast.c3
-rw-r--r--kernel/time/tick-common.c5
-rw-r--r--kernel/time/tick-sched.c296
-rw-r--r--kernel/timer.c16
16 files changed, 607 insertions, 88 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3820e3cefba..6b41c1899a8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -18,6 +18,7 @@
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/hash.h>
+#include <linux/tick.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
@@ -685,8 +686,12 @@ static void perf_pmu_rotate_start(struct pmu *pmu)
WARN_ON(!irqs_disabled());
- if (list_empty(&cpuctx->rotation_list))
+ if (list_empty(&cpuctx->rotation_list)) {
+ int was_empty = list_empty(head);
list_add(&cpuctx->rotation_list, head);
+ if (was_empty)
+ tick_nohz_full_kick();
+ }
}
static void get_ctx(struct perf_event_context *ctx)
@@ -2591,6 +2596,16 @@ done:
list_del_init(&cpuctx->rotation_list);
}
+#ifdef CONFIG_NO_HZ_FULL
+bool perf_event_can_stop_tick(void)
+{
+ if (list_empty(&__get_cpu_var(rotation_list)))
+ return true;
+ else
+ return false;
+}
+#endif
+
void perf_event_task_tick(void)
{
struct list_head *head = &__get_cpu_var(rotation_list);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 609d8ff38b7..fd4b13b131f 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -172,7 +172,7 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
*/
static int hrtimer_get_target(int this_cpu, int pinned)
{
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu))
return get_nohz_timer_target();
#endif
@@ -1125,7 +1125,7 @@ ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
}
EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/**
* hrtimer_get_next_event - get the time until next expiry event
*
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 8fd709c9bb5..42670e9b44e 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -10,6 +10,8 @@
#include <linux/kernel_stat.h>
#include <trace/events/timer.h>
#include <linux/random.h>
+#include <linux/tick.h>
+#include <linux/workqueue.h>
/*
* Called after updating RLIMIT_CPU to run cpu timer and update
@@ -153,6 +155,21 @@ static void bump_cpu_timer(struct k_itimer *timer,
}
}
+/**
+ * task_cputime_zero - Check a task_cputime struct for all zero fields.
+ *
+ * @cputime: The struct to compare.
+ *
+ * Checks @cputime to see if all fields are zero. Returns true if all fields
+ * are zero, false if any field is nonzero.
+ */
+static inline int task_cputime_zero(const struct task_cputime *cputime)
+{
+ if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
+ return 1;
+ return 0;
+}
+
static inline cputime_t prof_ticks(struct task_struct *p)
{
cputime_t utime, stime;
@@ -636,6 +653,37 @@ static int cpu_timer_sample_group(const clockid_t which_clock,
return 0;
}
+#ifdef CONFIG_NO_HZ_FULL
+static void nohz_kick_work_fn(struct work_struct *work)
+{
+ tick_nohz_full_kick_all();
+}
+
+static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);
+
+/*
+ * We need the IPIs to be sent from sane process context.
+ * The posix cpu timers are always set with irqs disabled.
+ */
+static void posix_cpu_timer_kick_nohz(void)
+{
+ schedule_work(&nohz_kick_work);
+}
+
+bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
+{
+ if (!task_cputime_zero(&tsk->cputime_expires))
+ return false;
+
+ if (tsk->signal->cputimer.running)
+ return false;
+
+ return true;
+}
+#else
+static inline void posix_cpu_timer_kick_nohz(void) { }
+#endif
+
/*
* Guts of sys_timer_settime for CPU timers.
* This is called with the timer locked and interrupts disabled.
@@ -794,6 +842,8 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
sample_to_timespec(timer->it_clock,
old_incr, &old->it_interval);
}
+ if (!ret)
+ posix_cpu_timer_kick_nohz();
return ret;
}
@@ -1008,21 +1058,6 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
}
}
-/**
- * task_cputime_zero - Check a task_cputime struct for all zero fields.
- *
- * @cputime: The struct to compare.
- *
- * Checks @cputime to see if all fields are zero. Returns true if all fields
- * are zero, false if any field is nonzero.
- */
-static inline int task_cputime_zero(const struct task_cputime *cputime)
-{
- if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
- return 1;
- return 0;
-}
-
/*
* Check for any per-thread CPU timers that have fired and move them
* off the tsk->*_timers list onto the firing list. Per-thread timers
@@ -1336,6 +1371,13 @@ void run_posix_cpu_timers(struct task_struct *tsk)
cpu_timer_fire(timer);
spin_unlock(&timer->it_lock);
}
+
+ /*
+ * In case some timers were rescheduled after the queue got emptied,
+ * wake up full dynticks CPUs.
+ */
+ if (tsk->signal->cputimer.running)
+ posix_cpu_timer_kick_nohz();
}
/*
@@ -1366,7 +1408,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
}
if (!*newval)
- return;
+ goto out;
*newval += now.cpu;
}
@@ -1384,6 +1426,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
tsk->signal->cputime_expires.virt_exp = *newval;
break;
}
+out:
+ posix_cpu_timer_kick_nohz();
}
static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d8534308fd0..16ea6792501 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -799,6 +799,16 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
rdp->offline_fqs++;
return 1;
}
+
+ /*
+ * There is a possibility that a CPU in adaptive-ticks state
+ * might run in the kernel with the scheduling-clock tick disabled
+ * for an extended time period. Invoke rcu_kick_nohz_cpu() to
+ * force the CPU to restart the scheduling-clock tick in this
+ * CPU is in this state.
+ */
+ rcu_kick_nohz_cpu(rdp->cpu);
+
return 0;
}
@@ -1820,7 +1830,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
struct rcu_node *rnp, struct rcu_data *rdp)
{
/* No-CBs CPUs do not have orphanable callbacks. */
- if (is_nocb_cpu(rdp->cpu))
+ if (rcu_is_nocb_cpu(rdp->cpu))
return;
/*
@@ -2892,10 +2902,10 @@ static void _rcu_barrier(struct rcu_state *rsp)
* corresponding CPU's preceding callbacks have been invoked.
*/
for_each_possible_cpu(cpu) {
- if (!cpu_online(cpu) && !is_nocb_cpu(cpu))
+ if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu))
continue;
rdp = per_cpu_ptr(rsp->rda, cpu);
- if (is_nocb_cpu(cpu)) {
+ if (rcu_is_nocb_cpu(cpu)) {
_rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
rsp->n_barrier_done);
atomic_inc(&rsp->barrier_cpu_count);
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 14ee40795d6..da77a8f57ff 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -530,13 +530,13 @@ static int rcu_nocb_needs_gp(struct rcu_state *rsp);
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp);
static void rcu_init_one_nocb(struct rcu_node *rnp);
-static bool is_nocb_cpu(int cpu);
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy);
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp);
+static void rcu_kick_nohz_cpu(int cpu);
static bool init_nocb_callback_list(struct rcu_data *rdp);
#endif /* #ifndef RCU_TREE_NONCORE */
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index d084ae3f281..170814dc418 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -28,6 +28,7 @@
#include <linux/gfp.h>
#include <linux/oom.h>
#include <linux/smpboot.h>
+#include <linux/tick.h>
#define RCU_KTHREAD_PRIO 1
@@ -1705,7 +1706,7 @@ static void rcu_prepare_for_idle(int cpu)
return;
/* If this is a no-CBs CPU, no callbacks, just return. */
- if (is_nocb_cpu(cpu))
+ if (rcu_is_nocb_cpu(cpu))
return;
/*
@@ -1747,7 +1748,7 @@ static void rcu_cleanup_after_idle(int cpu)
struct rcu_data *rdp;
struct rcu_state *rsp;
- if (is_nocb_cpu(cpu))
+ if (rcu_is_nocb_cpu(cpu))
return;
rcu_try_advance_all_cbs();
for_each_rcu_flavor(rsp) {
@@ -2052,7 +2053,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
}
/* Is the specified CPU a no-CPUs CPU? */
-static bool is_nocb_cpu(int cpu)
+bool rcu_is_nocb_cpu(int cpu)
{
if (have_rcu_nocb_mask)
return cpumask_test_cpu(cpu, rcu_nocb_mask);
@@ -2110,7 +2111,7 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy)
{
- if (!is_nocb_cpu(rdp->cpu))
+ if (!rcu_is_nocb_cpu(rdp->cpu))
return 0;
__call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy);
if (__is_kfree_rcu_offset((unsigned long)rhp->func))
@@ -2134,7 +2135,7 @@ static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
long qll = rsp->qlen_lazy;
/* If this is not a no-CBs CPU, tell the caller to do it the old way. */
- if (!is_nocb_cpu(smp_processor_id()))
+ if (!rcu_is_nocb_cpu(smp_processor_id()))
return 0;
rsp->qlen = 0;
rsp->qlen_lazy = 0;
@@ -2306,11 +2307,6 @@ static void rcu_init_one_nocb(struct rcu_node *rnp)
{
}
-static bool is_nocb_cpu(int cpu)
-{
- return false;
-}
-
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
bool lazy)
{
@@ -2337,3 +2333,20 @@ static bool init_nocb_callback_list(struct rcu_data *rdp)
}
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
+
+/*
+ * An adaptive-ticks CPU can potentially execute in kernel mode for an
+ * arbitrarily long period of time with the scheduling-clock tick turned
+ * off. RCU will be paying attention to this CPU because it is in the
+ * kernel, but the CPU cannot be guaranteed to be executing the RCU state
+ * machine because the scheduling-clock tick has been disabled. Therefore,
+ * if an adaptive-ticks CPU is failing to respond to the current grace
+ * period and has not be idle from an RCU perspective, kick it.
+ */
+static void rcu_kick_nohz_cpu(int cpu)
+{
+#ifdef CONFIG_NO_HZ_FULL
+ if (tick_nohz_full_cpu(cpu))
+ smp_send_reschedule(cpu);
+#endif /* #ifdef CONFIG_NO_HZ_FULL */
+}
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5662f58f0b6..58453b8272f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -544,7 +544,7 @@ void resched_cpu(int cpu)
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* In the semi idle case, use the nearest busy cpu for migrating timers
* from an idle cpu. This is good for power-savings.
@@ -582,7 +582,7 @@ unlock:
* account when the CPU goes back to idle and evaluates the timer
* wheel for the next timer event.
*/
-void wake_up_idle_cpu(int cpu)
+static void wake_up_idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
@@ -612,20 +612,56 @@ void wake_up_idle_cpu(int cpu)
smp_send_reschedule(cpu);
}
+static bool wake_up_full_nohz_cpu(int cpu)
+{
+ if (tick_nohz_full_cpu(cpu)) {
+ if (cpu != smp_processor_id() ||
+ tick_nohz_tick_stopped())
+ smp_send_reschedule(cpu);
+ return true;
+ }
+
+ return false;
+}
+
+void wake_up_nohz_cpu(int cpu)
+{
+ if (!wake_up_full_nohz_cpu(cpu))
+ wake_up_idle_cpu(cpu);
+}
+
static inline bool got_nohz_idle_kick(void)
{
int cpu = smp_processor_id();
return idle_cpu(cpu) && test_bit(NOHZ_BALANCE_KICK, nohz_flags(cpu));
}
-#else /* CONFIG_NO_HZ */
+#else /* CONFIG_NO_HZ_COMMON */
static inline bool got_nohz_idle_kick(void)
{
return false;
}
-#endif /* CONFIG_NO_HZ */
+#endif /* CONFIG_NO_HZ_COMMON */
+
+#ifdef CONFIG_NO_HZ_FULL
+bool sched_can_stop_tick(void)
+{
+ struct rq *rq;
+
+ rq = this_rq();
+
+ /* Make sure rq->nr_running update is visible after the IPI */
+ smp_rmb();
+
+ /* More than one running task need preemption */
+ if (rq->nr_running > 1)
+ return false;
+
+ return true;
+}
+#endif /* CONFIG_NO_HZ_FULL */
void sched_avg_update(struct rq *rq)
{
@@ -1357,7 +1393,8 @@ static void sched_ttwu_pending(void)
void scheduler_ipi(void)
{
- if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
+ if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()
+ && !tick_nohz_full_cpu(smp_processor_id()))
return;
/*
@@ -1374,6 +1411,7 @@ void scheduler_ipi(void)
* somewhat pessimize the simple resched case.
*/
irq_enter();
+ tick_nohz_full_check();
sched_ttwu_pending();
/*
@@ -1855,6 +1893,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
kprobe_flush_task(prev);
put_task_struct(prev);
}
+
+ tick_nohz_task_switch(current);
}
#ifdef CONFIG_SMP
@@ -2118,7 +2158,7 @@ calc_load(unsigned long load, unsigned long exp, unsigned long active)
return load >> FSHIFT;
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* Handle NO_HZ for the global load-average.
*
@@ -2344,12 +2384,12 @@ static void calc_global_nohz(void)
smp_wmb();
calc_load_idx++;
}
-#else /* !CONFIG_NO_HZ */
+#else /* !CONFIG_NO_HZ_COMMON */
static inline long calc_load_fold_idle(void) { return 0; }
static inline void calc_global_nohz(void) { }
-#endif /* CONFIG_NO_HZ */
+#endif /* CONFIG_NO_HZ_COMMON */
/*
* calc_load - update the avenrun load estimates 10 ticks after the
@@ -2509,7 +2549,7 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
sched_avg_update(this_rq);
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* There is no sane way to deal with nohz on smp when using jiffies because the
* cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
@@ -2569,7 +2609,7 @@ void update_cpu_load_nohz(void)
}
raw_spin_unlock(&this_rq->lock);
}
-#endif /* CONFIG_NO_HZ */
+#endif /* CONFIG_NO_HZ_COMMON */
/*
* Called from scheduler_tick()
@@ -2696,7 +2736,34 @@ void scheduler_tick(void)
rq->idle_balance = idle_cpu(cpu);
trigger_load_balance(rq, cpu);
#endif
+ rq_last_tick_reset(rq);
+}
+
+#ifdef CONFIG_NO_HZ_FULL
+/**
+ * scheduler_tick_max_deferment
+ *
+ * Keep at least one tick per second when a single
+ * active task is running because the scheduler doesn't
+ * yet completely support full dynticks environment.
+ *
+ * This makes sure that uptime, CFS vruntime, load
+ * balancing, etc... continue to move forward, even
+ * with a very low granularity.
+ */
+u64 scheduler_tick_max_deferment(void)
+{
+ struct rq *rq = this_rq();
+ unsigned long next, now = ACCESS_ONCE(jiffies);
+
+ next = rq->last_sched_tick + HZ;
+
+ if (time_before_eq(next, now))
+ return 0;
+
+ return jiffies_to_usecs(next - now) * NSEC_PER_USEC;
}
+#endif
notrace unsigned long get_parent_ip(unsigned long addr)
{
@@ -6951,9 +7018,12 @@ void __init sched_init(void)
INIT_LIST_HEAD(&rq->cfs_tasks);
rq_attach_root(rq, &def_root_domain);
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
rq->nohz_flags = 0;
#endif
+#ifdef CONFIG_NO_HZ_FULL
+ rq->last_sched_tick = 0;
+#endif
#endif
init_rq_hrtick(rq);
atomic_set(&rq->nr_iowait, 0);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8bf7081b1ec..c61a614465c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5355,7 +5355,7 @@ out_unlock:
return 0;
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* idle load balancing details
* - When one of the busy CPUs notice that there may be an idle rebalancing
@@ -5572,9 +5572,9 @@ out:
rq->next_balance = next_balance;
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
- * In CONFIG_NO_HZ case, the idle balance kickee will do the
+ * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
* rebalancing for all the cpus for whom scheduler ticks are stopped.
*/
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
@@ -5717,7 +5717,7 @@ void trigger_load_balance(struct rq *rq, int cpu)
if (time_after_eq(jiffies, rq->next_balance) &&
likely(!on_null_domain(cpu)))
raise_softirq(SCHED_SOFTIRQ);
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
nohz_balancer_kick(cpu);
#endif
@@ -6187,7 +6187,7 @@ __init void init_sched_fair_class(void)
#ifdef CONFIG_SMP
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
nohz.next_balance = jiffies;
zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
cpu_notifier(sched_ilb_notifier, 0);
diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
index b8ce7732834..d8da01008d3 100644
--- a/kernel/sched/idle_task.c
+++ b/kernel/sched/idle_task.c
@@ -17,6 +17,7 @@ select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
static void pre_schedule_idle(struct rq *rq, struct task_struct *prev)
{
idle_exit_fair(rq);
+ rq_last_tick_reset(rq);
}
static void post_schedule_idle(struct rq *rq)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4c225c4c711..ce39224d615 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -5,6 +5,7 @@
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/stop_machine.h>
+#include <linux/tick.h>
#include "cpupri.h"
#include "cpuacct.h"
@@ -405,10 +406,13 @@ struct rq {
#define CPU_LOAD_IDX_MAX 5
unsigned long cpu_load[CPU_LOAD_IDX_MAX];
unsigned long last_load_update_tick;
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
u64 nohz_stamp;
unsigned long nohz_flags;
#endif
+#ifdef CONFIG_NO_HZ_FULL
+ unsigned long last_sched_tick;
+#endif
int skip_clock_update;
/* capture load from *all* tasks on this cpu: */
@@ -1072,6 +1076,16 @@ static inline u64 steal_ticks(u64 steal)
static inline void inc_nr_running(struct rq *rq)
{
rq->nr_running++;
+
+#ifdef CONFIG_NO_HZ_FULL
+ if (rq->nr_running == 2) {
+ if (tick_nohz_full_cpu(rq->cpu)) {
+ /* Order rq->nr_running write against the IPI */
+ smp_wmb();
+ smp_send_reschedule(rq->cpu);
+ }
+ }
+#endif
}
static inline void dec_nr_running(struct rq *rq)
@@ -1079,6 +1093,13 @@ static inline void dec_nr_running(struct rq *rq)
rq->nr_running--;
}
+static inline void rq_last_tick_reset(struct rq *rq)
+{
+#ifdef CONFIG_NO_HZ_FULL
+ rq->last_sched_tick = jiffies;
+#endif
+}
+
extern void update_rq_clock(struct rq *rq);
extern void activate_task(struct rq *rq, struct task_struct *p, int flags);
@@ -1299,7 +1320,7 @@ extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
extern void account_cfs_bandwidth_used(int enabled, int was_enabled);
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
enum rq_nohz_flag_bits {
NOHZ_TICK_STOPPED,
NOHZ_BALANCE_KICK,
diff --git a/kernel/softirq.c b/kernel/softirq.c
index aa82723c720..b5197dcb0da 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -329,6 +329,19 @@ static inline void invoke_softirq(void)
wakeup_softirqd();
}
+static inline void tick_irq_exit(void)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+ int cpu = smp_processor_id();
+
+ /* Make sure that timer wheel updates are propagated */
+ if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
+ if (!in_interrupt())
+ tick_nohz_irq_exit();
+ }
+#endif
+}
+
/*
* Exit an interrupt context. Process softirqs if needed and possible:
*/
@@ -346,11 +359,7 @@ void irq_exit(void)
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();
-#ifdef CONFIG_NO_HZ
- /* Make sure that timer wheel updates are propagated */
- if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
- tick_nohz_irq_exit();
-#endif
+ tick_irq_exit();
rcu_irq_exit();
}
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 24510d84efd..e4c07b0692b 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -64,20 +64,88 @@ config GENERIC_CMOS_UPDATE
if GENERIC_CLOCKEVENTS
menu "Timers subsystem"
-# Core internal switch. Selected by NO_HZ / HIGH_RES_TIMERS. This is
+# Core internal switch. Selected by NO_HZ_COMMON / HIGH_RES_TIMERS. This is
# only related to the tick functionality. Oneshot clockevent devices
# are supported independ of this.
config TICK_ONESHOT
bool
-config NO_HZ
- bool "Tickless System (Dynamic Ticks)"
+config NO_HZ_COMMON
+ bool
depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
select TICK_ONESHOT
+
+choice
+ prompt "Timer tick handling"
+ default NO_HZ_IDLE if NO_HZ
+
+config HZ_PERIODIC
+ bool "Periodic timer ticks (constant rate, no dynticks)"
+ help
+ This option keeps the tick running periodically at a constant
+ rate, even when the CPU doesn't need it.
+
+config NO_HZ_IDLE
+ bool "Idle dynticks system (tickless idle)"
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ select NO_HZ_COMMON
+ help
+ This option enables a tickless idle system: timer interrupts
+ will only trigger on an as-needed basis when the system is idle.
+ This is usually interesting for energy saving.
+
+ Most of the time you want to say Y here.
+
+config NO_HZ_FULL
+ bool "Full dynticks system (tickless)"
+ # NO_HZ_COMMON dependency
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
+ # We need at least one periodic CPU for timekeeping
+ depends on SMP
+ # RCU_USER_QS dependency
+ depends on HAVE_CONTEXT_TRACKING
+ # VIRT_CPU_ACCOUNTING_GEN dependency
+ depends on 64BIT
+ select NO_HZ_COMMON
+ select RCU_USER_QS
+ select RCU_NOCB_CPU
+ select VIRT_CPU_ACCOUNTING_GEN
+ select CONTEXT_TRACKING_FORCE
+ select IRQ_WORK
+ help
+ Adaptively try to shutdown the tick whenever possible, even when
+ the CPU is running tasks. Typically this requires running a single
+ task on the CPU. Chances for running tickless are maximized when
+ the task mostly runs in userspace and has few kernel activity.
+
+ You need to fill up the nohz_full boot parameter with the
+ desired range of dynticks CPUs.
+
+ This is implemented at the expense of some overhead in user <-> kernel
+ transitions: syscalls, exceptions and interrupts. Even when it's
+ dynamically off.
+
+ Say N.
+
+endchoice
+
+config NO_HZ_FULL_ALL
+ bool "Full dynticks system on all CPUs by default"
+ depends on NO_HZ_FULL
+ help
+ If the user doesn't pass the nohz_full boot option to
+ define the range of full dynticks CPUs, consider that all
+ CPUs in the system are full dynticks by default.
+ Note the boot CPU will still be kept outside the range to
+ handle the timekeeping duty.
+
+config NO_HZ
+ bool "Old Idle dynticks config"
+ depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS
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.
+ This is the old config entry that enables dynticks idle.
+ We keep it around for a little while to enforce backward
+ compatibility with older config files.
config HIGH_RES_TIMERS
bool "High Resolution Timer Support"
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 61d00a8cdf2..206bbfb34e0 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -693,7 +693,8 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
bc->event_handler = tick_handle_oneshot_broadcast;
/* Take the do_timer update */
- tick_do_timer_cpu = cpu;
+ if (!tick_nohz_full_cpu(cpu))
+ tick_do_timer_cpu = cpu;
/*
* We must be careful here. There might be other CPUs
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 6176a3e4570..5d3fb100bc0 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -163,7 +163,10 @@ static void tick_setup_device(struct tick_device *td,
* this cpu:
*/
if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
- tick_do_timer_cpu = cpu;
+ if (!tick_nohz_full_cpu(cpu))
+ tick_do_timer_cpu = cpu;
+ else
+ tick_do_timer_cpu = TICK_DO_TIMER_NONE;
tick_next_period = ktime_get();
tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
}
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);
diff --git a/kernel/timer.c b/kernel/timer.c
index 09bca8ce977..a860bba3441 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -739,7 +739,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
cpu = smp_processor_id();
-#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
+#if defined(CONFIG_NO_HZ_COMMON) && defined(CONFIG_SMP)
if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
cpu = get_nohz_timer_target();
#endif
@@ -931,14 +931,14 @@ void add_timer_on(struct timer_list *timer, int cpu)
debug_activate(timer, timer->expires);
internal_add_timer(base, timer);
/*
- * Check whether the other CPU is idle and needs to be
- * triggered to reevaluate the timer wheel when nohz is
- * active. We are protected against the other CPU fiddling
+ * Check whether the other CPU is in dynticks mode and needs
+ * to be triggered to reevaluate the timer wheel.
+ * We are protected against the other CPU fiddling
* with the timer by holding the timer base lock. This also
- * makes sure that a CPU on the way to idle can not evaluate
- * the timer wheel.
+ * makes sure that a CPU on the way to stop its tick can not
+ * evaluate the timer wheel.
*/
- wake_up_idle_cpu(cpu);
+ wake_up_nohz_cpu(cpu);
spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);
@@ -1189,7 +1189,7 @@ static inline void __run_timers(struct tvec_base *base)
spin_unlock_irq(&base->lock);
}
-#ifdef CONFIG_NO_HZ
+#ifdef CONFIG_NO_HZ_COMMON
/*
* Find out when the next timer event is due to happen. This
* is used on S/390 to stop all activity when a CPU is idle.