[RFCv3 PATCH 47/48] sched: Enable active migration for cpus of lower capacity

[Morten Rasmussen]

Add an extra criteria to need_active_balance() to kick off active load
balance if the source cpu is overutilized and has lower capacity than
the destination cpus.

cc: Ingo Molnar <mingo@xxxxxxxxxx>
cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

Signed-off-by: Morten Rasmussen <morten.rasmussen@xxxxxxx>
---
 kernel/sched/fair.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 92fd1d8..1c248f8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7379,6 +7379,13 @@ static int need_active_balance(struct lb_env *env)
 			return 1;
 	}
 
+	if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
+				env->src_rq->cfs.h_nr_running == 1 &&
+				cpu_overutilized(env->src_cpu, env->sd) &&
+				!cpu_overutilized(env->dst_cpu, env->sd)) {
+			return 1;
+	}
+
 	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
 }
 
-- 
1.9.1

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