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: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1236603381.8389.455.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -331,6 +331,13 @@ static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
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*/
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static DEFINE_SPINLOCK(task_group_lock);
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#ifdef CONFIG_SMP
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static int root_task_group_empty(void)
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{
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return list_empty(&root_task_group.children);
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}
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#endif
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#ifdef CONFIG_FAIR_GROUP_SCHED
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#ifdef CONFIG_USER_SCHED
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# define INIT_TASK_GROUP_LOAD (2*NICE_0_LOAD)
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@ -391,6 +398,13 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
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#else
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#ifdef CONFIG_SMP
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static int root_task_group_empty(void)
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{
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return 1;
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}
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#endif
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static inline void set_task_rq(struct task_struct *p, unsigned int cpu) { }
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static inline struct task_group *task_group(struct task_struct *p)
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{
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@ -2318,7 +2332,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
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sync = 0;
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#ifdef CONFIG_SMP
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if (sched_feat(LB_WAKEUP_UPDATE)) {
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if (sched_feat(LB_WAKEUP_UPDATE) && !root_task_group_empty()) {
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struct sched_domain *sd;
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this_cpu = raw_smp_processor_id();
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