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Commit 57310a98 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: optimize ttwu vs group scheduling 



Impact: micro-optimization

We can avoid the sched domain walk on try_to_wake_up() when we know
there are no groups.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1236603381.8389.455.camel@laptop>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8c54436a

kernel/sched.c

+15 −1
Original line number Diff line number Diff line
@@ -331,6 +331,13 @@ static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp; 
 */

static DEFINE_SPINLOCK(task_group_lock);



#ifdef CONFIG_SMP

static int root_task_group_empty(void)

{

	return list_empty(&root_task_group.children);

}

#endif



#ifdef CONFIG_FAIR_GROUP_SCHED

#ifdef CONFIG_USER_SCHED

# define INIT_TASK_GROUP_LOAD	(2*NICE_0_LOAD)
@@ -391,6 +398,13 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu) 


#else



#ifdef CONFIG_SMP

static int root_task_group_empty(void)

{

	return 1;

}

#endif



static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }

static inline struct task_group *task_group(struct task_struct *p)

{
@@ -2318,7 +2332,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync) 
		sync = 0;



#ifdef CONFIG_SMP

	if (sched_feat(LB_WAKEUP_UPDATE)) {

	if (sched_feat(LB_WAKEUP_UPDATE) && !root_task_group_empty()) {

		struct sched_domain *sd;



		this_cpu = raw_smp_processor_id();