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authorFrederic Weisbecker <fweisbec@gmail.com>2013-07-10 04:44:35 +0400
committerFrederic Weisbecker <fweisbec@gmail.com>2013-08-14 19:14:45 +0400
commitad65782fba507d91a0a98f519b59e79cac1b474c (patch)
tree72e075f00818a0e29bc0874a0ce9ae48c5784614 /include/linux/context_tracking.h
parent65f382fd0c8fa483713c0971de9f1dfb4cf1ad9c (diff)
downloadlinux-ad65782fba507d91a0a98f519b59e79cac1b474c.tar.xz
context_tracking: Optimize main APIs off case with static key
Optimize user and exception 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 to be nopped (at least we hope so...). If this proves not be enough in the long term, we'll need to bring an exception slow path by re-routing the exception handlers. 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>
Diffstat (limited to 'include/linux/context_tracking.h')
-rw-r--r--include/linux/context_tracking.h27
1 files changed, 22 insertions, 5 deletions
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index c138c24bad1a..38ab60b3f3a6 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -38,23 +38,40 @@ static inline bool context_tracking_active(void)
extern void context_tracking_cpu_set(int cpu);
-extern void user_enter(void);
-extern void user_exit(void);
+extern void context_tracking_user_enter(void);
+extern void context_tracking_user_exit(void);
+
+static inline void user_enter(void)
+{
+ if (static_key_false(&context_tracking_enabled))
+ context_tracking_user_enter();
+
+}
+static inline void user_exit(void)
+{
+ if (static_key_false(&context_tracking_enabled))
+ context_tracking_user_exit();
+}
static inline enum ctx_state exception_enter(void)
{
enum ctx_state prev_ctx;
+ if (!static_key_false(&context_tracking_enabled))
+ return 0;
+
prev_ctx = this_cpu_read(context_tracking.state);
- user_exit();
+ context_tracking_user_exit();
return prev_ctx;
}
static inline void exception_exit(enum ctx_state prev_ctx)
{
- if (prev_ctx == IN_USER)
- user_enter();
+ if (static_key_false(&context_tracking_enabled)) {
+ if (prev_ctx == IN_USER)
+ context_tracking_user_enter();
+ }
}
extern void context_tracking_task_switch(struct task_struct *prev,