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| author | Peter Zijlstra <peterz@infradead.org> | 2009-03-09 13:56:21 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-03-10 16:43:36 +0100 |
| commit | 57310a98a354e84279d7c8af2f48805a62372e53 (patch) | |
| tree | e0027f76f0d48da80f49cf6948de860402572837 /kernel/sched.c | |
| parent | 8c54436ae9f59146b3d02820a3ebbf71e61f2aee (diff) | |
| download | lwn-57310a98a354e84279d7c8af2f48805a62372e53.tar.gz lwn-57310a98a354e84279d7c8af2f48805a62372e53.zip | |
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>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index e0fa739a441b..af5cd1b2d03e 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -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(); |