1 files changed, 42 insertions, 13 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1b12b14756ec..14c8527d7bcb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -51,6 +51,7 @@
 unsigned int sysctl_sched_latency = 6000000ULL;
 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
 
+unsigned int sysctl_sched_cstate_aware = 1;
 /*
  * The initial- and re-scaling of tunables is configurable
  * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
@@ -5468,15 +5469,20 @@ static int select_idle_sibling(struct task_struct *p, int target)
 	struct sched_domain *sd;
 	struct sched_group *sg;
 	int i = task_cpu(p);
+	int best_idle = -1;
+	int best_idle_cstate = -1;
+	int best_idle_capacity = INT_MAX;
 
-	if (idle_cpu(target))
-		return target;
+	if (!sysctl_sched_cstate_aware) {
+		if (idle_cpu(target))
+			return target;
 
-	/*
-	 * If the prevous cpu is cache affine and idle, don't be stupid.
-	 */
-	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
-		return i;
+		/*
+		 * If the prevous cpu is cache affine and idle, don't be stupid.
+		 */
+		if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
+			return i;
+	}
 
 	/*
 	 * Otherwise, iterate the domains and find an elegible idle cpu.
@@ -5489,18 +5495,41 @@ static int select_idle_sibling(struct task_struct *p, int target)
 						tsk_cpus_allowed(p)))
 				goto next;
 
-			for_each_cpu(i, sched_group_cpus(sg)) {
-				if (i == target || !idle_cpu(i))
-					goto next;
-			}
+			if (sysctl_sched_cstate_aware) {
+				for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg)) {
+					struct rq *rq = cpu_rq(i);
+					int idle_idx = idle_get_state_idx(rq);
+					unsigned long new_usage = boosted_task_util(p);
+					unsigned long capacity_orig = capacity_orig_of(i);
+					if (new_usage > capacity_orig || !idle_cpu(i))
+						goto next;
+
+					if (i == target && new_usage <= capacity_curr_of(target))
+						return target;
+
+					if (best_idle < 0 || (idle_idx < best_idle_cstate && capacity_orig <= best_idle_capacity)) {
+						best_idle = i;
+						best_idle_cstate = idle_idx;
+						best_idle_capacity = capacity_orig;
+					}
+				}
+			} else {
+				for_each_cpu(i, sched_group_cpus(sg)) {
+					if (i == target || !idle_cpu(i))
+						goto next;
+				}
 
-			target = cpumask_first_and(sched_group_cpus(sg),
+				target = cpumask_first_and(sched_group_cpus(sg),
 					tsk_cpus_allowed(p));
-			goto done;
+				goto done;
+			}
 next:
 			sg = sg->next;
 		} while (sg != sd->groups);
 	}
+	if (best_idle > 0)
+		target = best_idle;
+
 done:
 	return target;
 }