sched/fair: Allow calculate_imbalance() to move idle cpus
Allow calculate_imbalance() to 'create' idle cpus in the busiest group
if there are idle cpus in the local group.
Suggested-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140729152705.GX12054@laptop.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9437725..df1ed17 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6273,12 +6273,11 @@
return fix_small_imbalance(env, sds);
}
- if (busiest->group_type == group_overloaded) {
- /*
- * Don't want to pull so many tasks that a group would go idle.
- * Except of course for the group_imb case, since then we might
- * have to drop below capacity to reach cpu-load equilibrium.
- */
+ /*
+ * If there aren't any idle cpus, avoid creating some.
+ */
+ if (busiest->group_type == group_overloaded &&
+ local->group_type == group_overloaded) {
load_above_capacity =
(busiest->sum_nr_running - busiest->group_capacity_factor);
