Commit-ID: 57310a98a354e84279d7c8af2f48805a62372e53
Gitweb: http://git.kernel.org/tip/57310a98a354e84279d7c8af2f48805a62372e53
Author: "Peter Zijlstra" <peterz@xxxxxxxxxxxxx>
AuthorDate: Mon, 9 Mar 2009 13:56:21 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
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@xxxxxxxxx>
LKML-Reference: <1236603381.8389.455.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
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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