nohz: Optimize full dynticks state checks with static keys

These APIs are frequenctly accessed and priority is given
to optimize the full dynticks off-case in order to let
distros enable this feature without suffering from
significant performance regressions.

Let's inline these APIs and optimize them with static keys.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Kevin Hilman <khilman@linaro.org>

1 files changed, 23 insertions, 2 deletions

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 9180f4b..c60b079 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -10,6 +10,8 @@
 #include <linux/irqflags.h>
 #include <linux/percpu.h>
 #include <linux/hrtimer.h>
+#include <linux/context_tracking_state.h>
+#include <linux/cpumask.h>
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 
@@ -158,15 +160,34 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
 # endif /* !CONFIG_NO_HZ_COMMON */
 
 #ifdef CONFIG_NO_HZ_FULL
+extern bool tick_nohz_full_running;
+extern cpumask_var_t tick_nohz_full_mask;
+
+static inline bool tick_nohz_full_enabled(void)
+{
+	if (!static_key_false(&context_tracking_enabled))
+		return false;
+
+	return tick_nohz_full_running;
+}
+
+static inline bool tick_nohz_full_cpu(int cpu)
+{
+	if (!tick_nohz_full_enabled())
+		return false;
+
+	return cpumask_test_cpu(cpu, tick_nohz_full_mask);
+}
+
 extern void tick_nohz_init(void);
-extern int tick_nohz_full_cpu(int cpu);
 extern void tick_nohz_full_check(void);
 extern void tick_nohz_full_kick(void);
 extern void tick_nohz_full_kick_all(void);
 extern void tick_nohz_task_switch(struct task_struct *tsk);
 #else
 static inline void tick_nohz_init(void) { }
-static inline int tick_nohz_full_cpu(int cpu) { return 0; }
+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_check(void) { }
 static inline void tick_nohz_full_kick(void) { }
 static inline void tick_nohz_full_kick_all(void) { }