sched: Ditch per cgroup task lists for load-balancing

Per cgroup load-balance has numerous problems, chief amongst them that
there is no real sane order in them. So stop pretending it makes sense
and enqueue all tasks on a single list.

This also allows us to more easily fix the fwd progress issue
uncovered by the lock-break stuff. Rotate the list on failure to
migreate and limit the total iterations to nr_running (which with
releasing the lock isn't strictly accurate but close enough).

Also add a filter that skips very light tasks on the first attempt
around the list, this attempts to avoid shooting whole cgroups around
without affecting over balance.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: pjt@google.com
Link: http://lkml.kernel.org/n/tip-tx8yqydc7eimgq7i4rkc3a4g@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 8 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c0660a1a0cd1..753bdd567416 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -212,9 +212,6 @@ struct cfs_rq {
 	struct rb_root tasks_timeline;
 	struct rb_node *rb_leftmost;
 
-	struct list_head tasks;
-	struct list_head *balance_iterator;
-
 	/*
 	 * 'curr' points to currently running entity on this cfs_rq.
 	 * It is set to NULL otherwise (i.e when none are currently running).
@@ -242,11 +239,6 @@ struct cfs_rq {
 
 #ifdef CONFIG_SMP
 	/*
-	 * the part of load.weight contributed by tasks
-	 */
-	unsigned long task_weight;
-
-	/*
 	 *   h_load = weight * f(tg)
 	 *
 	 * Where f(tg) is the recursive weight fraction assigned to
@@ -420,6 +412,8 @@ struct rq {
 	int cpu;
 	int online;
 
+	struct list_head cfs_tasks;
+
 	u64 rt_avg;
 	u64 age_stamp;
 	u64 idle_stamp;