1 files changed, 56 insertions, 0 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a0ce83e835a..6fb47a2f7383 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5897,6 +5897,40 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 }
 
 /*
+ * Scan the asym_capacity domain for idle CPUs; pick the first idle one on which
+ * the task fits. If no CPU is big enough, but there are idle ones, try to
+ * maximize capacity.
+ */
+static int
+select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target)
+{
+	unsigned long best_cap = 0;
+	int cpu, best_cpu = -1;
+	struct cpumask *cpus;
+
+	sync_entity_load_avg(&p->se);
+
+	cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
+	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+
+	for_each_cpu_wrap(cpu, cpus, target) {
+		unsigned long cpu_cap = capacity_of(cpu);
+
+		if (!available_idle_cpu(cpu) && !sched_idle_cpu(cpu))
+			continue;
+		if (task_fits_capacity(p, cpu_cap))
+			return cpu;
+
+		if (cpu_cap > best_cap) {
+			best_cap = cpu_cap;
+			best_cpu = cpu;
+		}
+	}
+
+	return best_cpu;
+}
+
+/*
  * Try and locate an idle core/thread in the LLC cache domain.
  */
 static int select_idle_sibling(struct task_struct *p, int prev, int target)
@@ -5904,6 +5938,28 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	struct sched_domain *sd;
 	int i, recent_used_cpu;
 
+	/*
+	 * For asymmetric CPU capacity systems, our domain of interest is
+	 * sd_asym_cpucapacity rather than sd_llc.
+	 */
+	if (static_branch_unlikely(&sched_asym_cpucapacity)) {
+		sd = rcu_dereference(per_cpu(sd_asym_cpucapacity, target));
+		/*
+		 * On an asymmetric CPU capacity system where an exclusive
+		 * cpuset defines a symmetric island (i.e. one unique
+		 * capacity_orig value through the cpuset), the key will be set
+		 * but the CPUs within that cpuset will not have a domain with
+		 * SD_ASYM_CPUCAPACITY. These should follow the usual symmetric
+		 * capacity path.
+		 */
+		if (!sd)
+			goto symmetric;
+
+		i = select_idle_capacity(p, sd, target);
+		return ((unsigned)i < nr_cpumask_bits) ? i : target;
+	}
+
+symmetric:
 	if (available_idle_cpu(target) || sched_idle_cpu(target))
 		return target;