Messages in this thread Patch in this message | | | Date | Tue, 10 Mar 2009 15:45:27 GMT | From | Peter Zijlstra <> | Subject | [tip:sched/core] sched: optimize ttwu vs group scheduling |
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Commit-ID: 57310a98a354e84279d7c8af2f48805a62372e53 Gitweb: http://git.kernel.org/tip/57310a98a354e84279d7c8af2f48805a62372e53 Author: "Peter Zijlstra" <peterz@infradead.org> AuthorDate: Mon, 9 Mar 2009 13:56:21 +0100 Commit: Ingo Molnar <mingo@elte.hu> CommitDate: Tue, 10 Mar 2009 16:43:36 +0100
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>
--- kernel/sched.c | 16 +++++++++++++++- 1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index e0fa739..af5cd1b 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();
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