context_tracking: Optimize guest APIs off case with static key

fweisbec · fweisbec · commit 48d6a816a8bf · 2013-08-14T17:14:46.000+02:00
Optimize guest entry/exit APIs with static keys. This minimize
the overhead for those who enable CONFIG_NO_HZ_FULL without
always using it. Having no range passed to nohz_full= should
result in the probes overhead to be minimized.

Signed-off-by: Frederic Weisbecker &lt;fweisbec@gmail.com&gt;
Cc: Steven Rostedt &lt;rostedt@goodmis.org&gt;
Cc: Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;
Cc: Ingo Molnar &lt;mingo@kernel.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Li Zhong &lt;zhong@linux.vnet.ibm.com&gt;
Cc: Mike Galbraith &lt;efault@gmx.de&gt;
Cc: Kevin Hilman &lt;khilman@linaro.org&gt;
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
@@ -95,8 +95,23 @@ static inline void context_tracking_init(void) { }
 
 
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
-extern void guest_enter(void);
-extern void guest_exit(void);
+static inline void guest_enter(void)
+{
+	if (static_key_false(&context_tracking_enabled) &&
+	    vtime_accounting_enabled())
+		vtime_guest_enter(current);
+	else
+		current->flags |= PF_VCPU;
+}
+
+static inline void guest_exit(void)
+{
+	if (static_key_false(&context_tracking_enabled) &&
+	    vtime_accounting_enabled())
+		vtime_guest_exit(current);
+	else
+		current->flags &= ~PF_VCPU;
+}
 #else
 static inline void guest_enter(void)
 {
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
@@ -21,8 +21,10 @@
 #include <linux/export.h>
 
 struct static_key context_tracking_enabled = STATIC_KEY_INIT_FALSE;
+EXPORT_SYMBOL_GPL(context_tracking_enabled);
 
 DEFINE_PER_CPU(struct context_tracking, context_tracking);
+EXPORT_SYMBOL_GPL(context_tracking);
 
 void context_tracking_cpu_set(int cpu)
 {
@@ -163,27 +165,6 @@ void context_tracking_user_exit(void)
 	local_irq_restore(flags);
 }
 
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
-void guest_enter(void)
-{
-	if (vtime_accounting_enabled())
-		vtime_guest_enter(current);
-	else
-		current->flags |= PF_VCPU;
-}
-EXPORT_SYMBOL_GPL(guest_enter);
-
-void guest_exit(void)
-{
-	if (vtime_accounting_enabled())
-		vtime_guest_exit(current);
-	else
-		current->flags &= ~PF_VCPU;
-}
-EXPORT_SYMBOL_GPL(guest_exit);
-#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
-
-
 /**
  * context_tracking_task_switch - context switch the syscall callbacks
  * @prev: the task that is being switched out
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
@@ -724,6 +724,7 @@ void vtime_guest_enter(struct task_struct *tsk)
 	current->flags |= PF_VCPU;
 	write_sequnlock(&tsk->vtime_seqlock);
 }
+EXPORT_SYMBOL_GPL(vtime_guest_enter);
 
 void vtime_guest_exit(struct task_struct *tsk)
 {
@@ -732,6 +733,7 @@ void vtime_guest_exit(struct task_struct *tsk)
 	current->flags &= ~PF_VCPU;
 	write_sequnlock(&tsk->vtime_seqlock);
 }
+EXPORT_SYMBOL_GPL(vtime_guest_exit);
 
 void vtime_account_idle(struct task_struct *tsk)
 {

Original file line number	Diff line number	Diff line change
`@@ -724,6 +724,7 @@ void vtime_guest_enter(struct task_struct *tsk)`
`724`	`724`	`current->flags \|= PF_VCPU;`
`725`	`725`	`write_sequnlock(&tsk->vtime_seqlock);`
`726`	`726`	`}`
	`727`	`+EXPORT_SYMBOL_GPL(vtime_guest_enter);`
`727`	`728`
`728`	`729`	`void vtime_guest_exit(struct task_struct *tsk)`
`729`	`730`	`{`
`@@ -732,6 +733,7 @@ void vtime_guest_exit(struct task_struct *tsk)`
`732`	`733`	`current->flags &= ~PF_VCPU;`
`733`	`734`	`write_sequnlock(&tsk->vtime_seqlock);`
`734`	`735`	`}`
	`736`	`+EXPORT_SYMBOL_GPL(vtime_guest_exit);`
`735`	`737`
`736`	`738`	`void vtime_account_idle(struct task_struct *tsk)`
`737`	`739`	`{`