From: Lukasz Luba <l.luba@partner.samsung.com>
Date: Thu, 23 Aug 2018 09:37:38 +0000 (+0200)
Subject: sched/fair: change migration destination based on CPU utilization
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6d03ea44fb8ea1e2487d19783d101ccbbfa5dfa9;p=platform%2Fkernel%2Flinux-exynos.git

sched/fair: change migration destination based on CPU utilization

The patch changes 'fitness' of the destination CPU during migration.
The destiation CPU can have lite utilization of around ~6% and
in that case the task utilization is neglected (since the src CPU
is allready overutilized).

Signed-off-by: Lukasz Luba <l.luba@partner.samsung.com>
---

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8ac2ad9a5b8d..d6c9e4b41330 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7616,7 +7616,7 @@ static inline bool check_cpu_spare_capacity(int cpu,
 					  unsigned int needed_spare_capacity)
 {
 	return (capacity_of(cpu) >
-		(cpu_util(cpu) + (needed_spare_capacity / 2)));
+		(cpu_util(cpu) + needed_spare_capacity));
 
 }
 
@@ -9105,6 +9105,12 @@ static struct rq *find_busiest_queue(struct lb_env *env,
  */
 #define MAX_PINNED_INTERVAL	512
 
+static inline bool check_cpu_lite_util(int cpu)
+{
+	/* Lite utilization is defined as less then ~6% */
+	return (capacity_of(cpu) >> 4 >= cpu_util(cpu));
+}
+
 static inline int need_park_into_spare_capacity(struct lb_env *env)
 {
 	bool fits_in = check_cpu_spare_capacity(env->dst_cpu,
@@ -9115,7 +9121,7 @@ static inline int need_park_into_spare_capacity(struct lb_env *env)
 				env->src_rq->cfs.h_nr_running == 1 &&
 				cpu_overutilized(env->src_cpu) &&
 				!cpu_overutilized(env->dst_cpu) &&
-				fits_in) {
+				(fits_in || check_cpu_lite_util(env->dst_cpu))) {
 		ret = 1;
 	} else {
 		ret = 0;