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context_tracking: Optimize guest APIs off case with static key 

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 <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>
This commit is contained in:
Frederic Weisbecker 2013-07-10 02:44:35 +02:00
parent ad65782fba
commit 48d6a816a8
3 changed files with 21 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
include/linux/context_tracking.h
View File

@ -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)
{

23
kernel/context_tracking.c
View File

@ -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

2
kernel/sched/cputime.c
View File

@ -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)
{