[RFCv3 PATCH 45/48] sched: Skip cpu as lb src which has one task and capacity gte the dst cpu

[Morten Rasmussen]

From: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>

Skip cpu as a potential src (costliest) in case it has only one task
running and its original capacity is greater than or equal to the
original capacity of the dst cpu.

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

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4849bad..b6e2e92 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7251,6 +7251,10 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 			};
 			unsigned long energy = sched_group_energy(&eenv);
 
+			if (rq->nr_running == 1 && capacity_orig_of(i) >=
+					capacity_orig_of(env->dst_cpu))
+				continue;
+
 			/*
 			 * We're looking for the minimal cpu efficiency
 			 * min(u_i / e_i), crosswise multiplication leads to
-- 
1.9.1

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