From: Todd Kjos <tkjos@google.com>
Date: Wed, 13 Jul 2016 23:13:47 +0000 (-0700)
Subject: sched: use util instead of capacity to select busy cpu
X-Git-Tag: firefly_0821_release~176^2~203
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=831623e6fe5ea7a8dc858b10f369882b6d4fa39f;p=firefly-linux-kernel-4.4.55.git

sched: use util instead of capacity to select busy cpu

If cpus are busy, the cpu selection algorithm was favoring
cpus with lower capacity. This can result in uneven packing
since there will be a bias toward the same cpu until there
is a capacity change. Instead use the utilization so there
is immediate feedback as tasks are assigned

BUG: 30115868

Change-Id: I0ac7ae3ab5d8f2f5a5838c29bb6da2c3e8ef44e8
---

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a45a6e1a692c..26c7e3fd332f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5614,7 +5614,7 @@ static inline int find_best_target(struct task_struct *p, bool boosted)
 {
 	int iter_cpu;
 	int target_cpu = -1;
-	int target_capacity = 0;
+	int target_util = 0;
 	int backup_capacity = 0;
 	int best_idle_cpu = -1;
 	int best_idle_cstate = INT_MAX;
@@ -5670,10 +5670,10 @@ static inline int find_best_target(struct task_struct *p, bool boosted)
 
 		if (new_util < cur_capacity) {
 			if (cpu_rq(i)->nr_running) {
-				if (target_capacity == 0 ||
-					target_capacity > cur_capacity) {
+				if (target_util == 0 ||
+					target_util > new_util) {
 					target_cpu = i;
-					target_capacity = cur_capacity;
+					target_util = new_util;
 				}
 			} else if (!boosted) {
 				if (best_idle_cpu < 0 ||