sched: Define sched_clock_irqtime as static key

Since CPU time accounting is a performance-critical path, let's define
sched_clock_irqtime as a static key to minimize potential overhead.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20250103022409.2544-2-laoar.shao@gmail.com

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 0bed0fa1acd988a0b29aed21fa9f77e908795029..5d9143dd087917ce8c4ce32276a713deffaba370 100644 (file)
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -9,6 +9,8 @@
 
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 
+DEFINE_STATIC_KEY_FALSE(sched_clock_irqtime);
+
 /*
  * There are no locks covering percpu hardirq/softirq time.
  * They are only modified in vtime_account, on corresponding CPU
@@ -22,16 +24,14 @@
  */
 DEFINE_PER_CPU(struct irqtime, cpu_irqtime);
 
-static int sched_clock_irqtime;
-
 void enable_sched_clock_irqtime(void)
 {
-       sched_clock_irqtime = 1;
+       static_branch_enable(&sched_clock_irqtime);
 }
 
 void disable_sched_clock_irqtime(void)
 {
-       sched_clock_irqtime = 0;
+       static_branch_disable(&sched_clock_irqtime);
 }
 
 static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
@@ -57,7 +57,7 @@ void irqtime_account_irq(struct task_struct *curr, unsigned int offset)
        s64 delta;
        int cpu;
 
-       if (!sched_clock_irqtime)
+       if (!irqtime_enabled())
                return;
 
        cpu = smp_processor_id();
@@ -90,8 +90,6 @@ static u64 irqtime_tick_accounted(u64 maxtime)
 
 #else /* CONFIG_IRQ_TIME_ACCOUNTING */
 
-#define sched_clock_irqtime    (0)
-
 static u64 irqtime_tick_accounted(u64 dummy)
 {
        return 0;
@@ -478,7 +476,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
        if (vtime_accounting_enabled_this_cpu())
                return;
 
-       if (sched_clock_irqtime) {
+       if (irqtime_enabled()) {
                irqtime_account_process_tick(p, user_tick, 1);
                return;
        }
@@ -507,7 +505,7 @@ void account_idle_ticks(unsigned long ticks)
 {
        u64 cputime, steal;
 
-       if (sched_clock_irqtime) {
+       if (irqtime_enabled()) {
                irqtime_account_idle_ticks(ticks);
                return;
        }

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 300db6fe53eb1119519ff133c8550723d0f6431d..3da237c934e776e64cf54da2f74fac5e834f2af5 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3233,6 +3233,12 @@ struct irqtime {
 };
 
 DECLARE_PER_CPU(struct irqtime, cpu_irqtime);
+DECLARE_STATIC_KEY_FALSE(sched_clock_irqtime);
+
+static inline int irqtime_enabled(void)
+{
+       return static_branch_likely(&sched_clock_irqtime);
+}
 
 /*
  * Returns the irqtime minus the softirq time computed by ksoftirqd.
@@ -3253,6 +3259,13 @@ static inline u64 irq_time_read(int cpu)
        return total;
 }
 
+#else
+
+static inline int irqtime_enabled(void)
+{
+       return 0;
+}
+
 #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
 
 #ifdef CONFIG_CPU_FREQ