sched: update placement logic to prefer C-state and busier CPUs

Update the wakeup placement logic when need_idle is not set. Break
ties in power with C-state. If C-state is the same break ties with
prev_cpu. Finally go for the most loaded CPU.

CRs-fixed: 1006303
Change-Id: Iafa98a909ed464af33f4fe3345bbfc8e77dee963
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>
[joonwoop@codeaurora.org: fixed bug where assigns best_cpu_cstate with
 uninitialized cpu_cstate.]
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>

1 files changed, 31 insertions, 6 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 11dc798e071a..b6e638bdcd98 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3138,7 +3138,7 @@ struct cluster_cpu_stats {
 	int best_capacity_cpu, best_cpu, best_sibling_cpu;
 	int min_cost, best_sibling_cpu_cost;
 	int best_cpu_cstate;
-	u64 min_load, best_sibling_cpu_load;
+	u64 min_load, max_load, best_sibling_cpu_load;
 	s64 highest_spare_capacity;
 };
 
@@ -3398,10 +3398,11 @@ static void update_cluster_stats(int cpu, struct cluster_cpu_stats *stats,
 		}
 	}
 
+	cpu_cstate = cpu_rq(cpu)->cstate;
+
 	if (env->need_idle) {
 		stats->min_cost = cpu_cost;
 		if (idle_cpu(cpu)) {
-			cpu_cstate = cpu_rq(cpu)->cstate;
 			if (cpu_cstate < stats->best_cpu_cstate ||
 				(cpu_cstate == stats->best_cpu_cstate &&
 							cpu == prev_cpu)) {
@@ -3420,11 +3421,34 @@ static void update_cluster_stats(int cpu, struct cluster_cpu_stats *stats,
 		return;
 	}
 
-	if ((cpu_cost < stats->min_cost) ||
-	    ((stats->best_cpu != prev_cpu && stats->min_load > env->cpu_load) ||
-	     cpu == prev_cpu)) {
+	if (cpu_cost < stats->min_cost)  {
 		stats->min_cost = cpu_cost;
-		stats->min_load = env->cpu_load;
+		stats->best_cpu_cstate = cpu_cstate;
+		stats->max_load = env->cpu_load;
+		stats->best_cpu = cpu;
+		return;
+	}
+
+	/* CPU cost is the same. Start breaking the tie by C-state */
+
+	if (cpu_cstate > stats->best_cpu_cstate)
+		return;
+
+	if (cpu_cstate < stats->best_cpu_cstate) {
+		stats->best_cpu_cstate = cpu_cstate;
+		stats->max_load = env->cpu_load;
+		stats->best_cpu = cpu;
+		return;
+	}
+
+	/* C-state is the same. Use prev CPU to break the tie */
+	if (cpu == prev_cpu) {
+		stats->best_cpu = cpu;
+		return;
+	}
+
+	if (stats->best_cpu != prev_cpu && env->cpu_load > stats->max_load) {
+		stats->max_load = env->cpu_load;
 		stats->best_cpu = cpu;
 	}
 }
@@ -3468,6 +3492,7 @@ static inline void init_cluster_cpu_stats(struct cluster_cpu_stats *stats)
 	stats->best_capacity_cpu = stats->best_sibling_cpu  = -1;
 	stats->min_cost = stats->best_sibling_cpu_cost = INT_MAX;
 	stats->min_load	= stats->best_sibling_cpu_load = ULLONG_MAX;
+	stats->max_load = 0;
 	stats->highest_spare_capacity = 0;
 	stats->least_loaded_cpu = -1;
 	stats->best_cpu_cstate = INT_MAX;