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authorFrederic Weisbecker <fweisbec@gmail.com>2015-06-07 16:54:30 +0300
committerFrederic Weisbecker <fweisbec@gmail.com>2016-03-02 18:41:39 +0300
commitd027d45d8a17a4145eab2d841140e9acbb7feb59 (patch)
tree492d0ffe0b6e2bc548266c382b8c5c41cb5ef3b8 /include/linux/tick.h
parent8537bb95a63e4be330359721f0ecd422f4a4c0ca (diff)
downloadlinux-d027d45d8a17a4145eab2d841140e9acbb7feb59.tar.xz
nohz: New tick dependency mask
The tick dependency is evaluated on every IRQ and context switch. This consists is a batch of checks which determine whether it is safe to stop the tick or not. These checks are often split in many details: posix cpu timers, scheduler, sched clock, perf events.... each of which are made of smaller details: posix cpu timer involves checking process wide timers then thread wide timers. Perf involves checking freq events then more per cpu details. Checking these informations asynchronously every time we update the full dynticks state bring avoidable overhead and a messy layout. Let's introduce instead tick dependency masks: one for system wide dependency (unstable sched clock, freq based perf events), one for CPU wide dependency (sched, throttling perf events), and task/signal level dependencies (posix cpu timers). The subsystems are responsible for setting and clearing their dependency through a set of APIs that will take care of concurrent dependency mask modifications and kick targets to restart the relevant CPU tick whenever needed. This new dependency engine stays beside the old one until all subsystems having a tick dependency are converted to it. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Suggested-by: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com> Cc: Christoph Lameter <cl@linux.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Diffstat (limited to 'include/linux/tick.h')
-rw-r--r--include/linux/tick.h92
1 files changed, 92 insertions, 0 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 97fd4e543846..d60e5df8ec28 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -97,6 +97,18 @@ static inline void tick_broadcast_exit(void)
tick_broadcast_oneshot_control(TICK_BROADCAST_EXIT);
}
+enum tick_dep_bits {
+ TICK_DEP_BIT_POSIX_TIMER = 0,
+ TICK_DEP_BIT_PERF_EVENTS = 1,
+ TICK_DEP_BIT_SCHED = 2,
+ TICK_DEP_BIT_CLOCK_UNSTABLE = 3
+};
+
+#define TICK_DEP_MASK_POSIX_TIMER (1 << TICK_DEP_BIT_POSIX_TIMER)
+#define TICK_DEP_MASK_PERF_EVENTS (1 << TICK_DEP_BIT_PERF_EVENTS)
+#define TICK_DEP_MASK_SCHED (1 << TICK_DEP_BIT_SCHED)
+#define TICK_DEP_MASK_CLOCK_UNSTABLE (1 << TICK_DEP_BIT_CLOCK_UNSTABLE)
+
#ifdef CONFIG_NO_HZ_COMMON
extern int tick_nohz_enabled;
extern int tick_nohz_tick_stopped(void);
@@ -154,6 +166,72 @@ static inline int housekeeping_any_cpu(void)
return cpumask_any_and(housekeeping_mask, cpu_online_mask);
}
+extern void tick_nohz_dep_set(enum tick_dep_bits bit);
+extern void tick_nohz_dep_clear(enum tick_dep_bits bit);
+extern void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit);
+extern void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit);
+extern void tick_nohz_dep_set_task(struct task_struct *tsk,
+ enum tick_dep_bits bit);
+extern void tick_nohz_dep_clear_task(struct task_struct *tsk,
+ enum tick_dep_bits bit);
+extern void tick_nohz_dep_set_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit);
+extern void tick_nohz_dep_clear_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit);
+
+/*
+ * The below are tick_nohz_[set,clear]_dep() wrappers that optimize off-cases
+ * on top of static keys.
+ */
+static inline void tick_dep_set(enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_set(bit);
+}
+
+static inline void tick_dep_clear(enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_clear(bit);
+}
+
+static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_cpu(cpu))
+ tick_nohz_dep_set_cpu(cpu, bit);
+}
+
+static inline void tick_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_cpu(cpu))
+ tick_nohz_dep_clear_cpu(cpu, bit);
+}
+
+static inline void tick_dep_set_task(struct task_struct *tsk,
+ enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_set_task(tsk, bit);
+}
+static inline void tick_dep_clear_task(struct task_struct *tsk,
+ enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_clear_task(tsk, bit);
+}
+static inline void tick_dep_set_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_set_signal(signal, bit);
+}
+static inline void tick_dep_clear_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit)
+{
+ if (tick_nohz_full_enabled())
+ tick_nohz_dep_clear_signal(signal, bit);
+}
+
extern void tick_nohz_full_kick(void);
extern void tick_nohz_full_kick_cpu(int cpu);
extern void tick_nohz_full_kick_all(void);
@@ -166,6 +244,20 @@ static inline int housekeeping_any_cpu(void)
static inline bool tick_nohz_full_enabled(void) { return false; }
static inline bool tick_nohz_full_cpu(int cpu) { return false; }
static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
+
+static inline void tick_dep_set(enum tick_dep_bits bit) { }
+static inline void tick_dep_clear(enum tick_dep_bits bit) { }
+static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline void tick_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { }
+static inline void tick_dep_set_task(struct task_struct *tsk,
+ enum tick_dep_bits bit) { }
+static inline void tick_dep_clear_task(struct task_struct *tsk,
+ enum tick_dep_bits bit) { }
+static inline void tick_dep_set_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit) { }
+static inline void tick_dep_clear_signal(struct signal_struct *signal,
+ enum tick_dep_bits bit) { }
+
static inline void tick_nohz_full_kick_cpu(int cpu) { }
static inline void tick_nohz_full_kick(void) { }
static inline void tick_nohz_full_kick_all(void) { }