sched: Implement on-demand (active) cfs_rq list

Make certain load-balance actions scale per number of active cgroups
instead of the number of existing cgroups.

This makes wakeup/sleep paths more expensive, but is a win for systems
where the vast majority of existing cgroups are idle.

Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101115234937.666535048@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 0 deletions

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index bea7d79f7e9c..c914ec747ca6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -183,6 +183,17 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
 }
 
+static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+        list_add_rcu(&rt_rq->leaf_rt_rq_list,
+                        &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
+}
+
+static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+        list_del_rcu(&rt_rq->leaf_rt_rq_list);
+}
+
 #define for_each_leaf_rt_rq(rt_rq, rq) \
         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
 
@@ -276,6 +287,14 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
         return ktime_to_ns(def_rt_bandwidth.rt_period);
 }
 
+static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+}
+
+static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
+{
+}
+
 #define for_each_leaf_rt_rq(rt_rq, rq) \
         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 
@@ -825,6 +844,9 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
                 return;
 
+        if (!rt_rq->rt_nr_running)
+                list_add_leaf_rt_rq(rt_rq);
+
         if (head)
                 list_add(&rt_se->run_list, queue);
         else
@@ -844,6 +866,8 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
 
         dec_rt_tasks(rt_se, rt_rq);
+        if (!rt_rq->rt_nr_running)
+                list_del_leaf_rt_rq(rt_rq);
 }
 
 /*