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Commit 48d6a816 authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

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: default avatarFrederic 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>
parent ad65782f

include/linux/context_tracking.h

+17 −2
Original line number Diff line number Diff line
@@ -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)

{

kernel/context_tracking.c

+2 −21
Original line number Diff line number Diff line
@@ -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

kernel/sched/cputime.c

+2 −0
Original line number Diff line number Diff line
@@ -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)

{