lkml.org 
[lkml]   [2013]   [Jul]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 10/21] context_tracking: Optimize context switch off case with static keys
Date
No need for syscall slowpath if no CPU is full dynticks,
rather nop this in this case.

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>
---
include/linux/context_tracking.h | 11 +++++++++--
kernel/context_tracking.c | 6 +++---
2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 03a32b0..66a8397 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -40,6 +40,8 @@ extern void context_tracking_cpu_set(int cpu);

extern void context_tracking_user_enter(void);
extern void context_tracking_user_exit(void);
+extern void __context_tracking_task_switch(struct task_struct *prev,
+ struct task_struct *next);

static inline void user_enter(void)
{
@@ -74,8 +76,12 @@ static inline void exception_exit(enum ctx_state prev_ctx)
}
}

-extern void context_tracking_task_switch(struct task_struct *prev,
- struct task_struct *next);
+static inline void context_tracking_task_switch(struct task_struct *prev,
+ struct task_struct *next)
+{
+ if (static_key_false(&context_tracking_enabled))
+ __context_tracking_task_switch(prev, next);
+}
#else
static inline bool context_tracking_in_user(void) { return false; }
static inline void user_enter(void) { }
@@ -104,6 +110,7 @@ static inline void guest_exit(void)
else
current->flags &= ~PF_VCPU;
}
+
#else
static inline void guest_enter(void)
{
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 5afa36b..ef21e4f 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -166,7 +166,7 @@ void context_tracking_user_exit(void)
}

/**
- * context_tracking_task_switch - context switch the syscall callbacks
+ * __context_tracking_task_switch - context switch the syscall callbacks
* @prev: the task that is being switched out
* @next: the task that is being switched in
*
@@ -178,8 +178,8 @@ void context_tracking_user_exit(void)
* migrate to some CPU that doesn't do the context tracking. As such the TIF
* flag may not be desired there.
*/
-void context_tracking_task_switch(struct task_struct *prev,
- struct task_struct *next)
+void __context_tracking_task_switch(struct task_struct *prev,
+ struct task_struct *next)
{
clear_tsk_thread_flag(prev, TIF_NOHZ);
set_tsk_thread_flag(next, TIF_NOHZ);
--
1.7.5.4


\
 
 \ /
  Last update: 2013-07-27 02:21    [W:0.153 / U:0.688 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site