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 a45a6e1a692c9a6e1f1823a7ce46c7cbb58accce..26c7e3fd332f7b8dfa0aad28c5c43595b8fa1f1b 100644 (file)
--- 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 ||