sched: Ignore offline CPUs in HMP migration & load statsmaster-task-placement-v2

Previously, an offline CPU would always appear to have a zero load
and this would distort the offload functionality used for balancing
big and little domains.

Maintain a mask of online CPUs in each domain and use this instead.

Change-Id: I639b564b2f40cb659af8ceb8bd37f84b8a1fe323
Signed-off-by: Chris Redpath <chris.redpath@arm.com>

3 files changed, 42 insertions, 4 deletions

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index f2ca9e03080..9047dd1c5a1 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -383,12 +383,14 @@ void __init arch_get_hmp_domains(struct list_head *hmp_domains_list)
 	if(!cpumask_empty(&hmp_slow_cpu_mask)) {
 		domain = (struct hmp_domain *)
 			kmalloc(sizeof(struct hmp_domain), GFP_KERNEL);
-		cpumask_copy(&domain->cpus, &hmp_slow_cpu_mask);
+		cpumask_copy(&domain->possible_cpus, &hmp_slow_cpu_mask);
+		cpumask_and(&domain->cpus, cpu_online_mask, &domain->possible_cpus);
 		list_add(&domain->hmp_domains, hmp_domains_list);
 	}
 	domain = (struct hmp_domain *)
 		kmalloc(sizeof(struct hmp_domain), GFP_KERNEL);
-	cpumask_copy(&domain->cpus, &hmp_fast_cpu_mask);
+	cpumask_copy(&domain->possible_cpus, &hmp_fast_cpu_mask);
+	cpumask_and(&domain->cpus, cpu_online_mask, &domain->possible_cpus);
 	list_add(&domain->hmp_domains, hmp_domains_list);
 }
 #endif /* CONFIG_SCHED_HMP */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5e903596e48..0e2a546cdad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -888,6 +888,7 @@ bool cpus_share_cache(int this_cpu, int that_cpu);
 #ifdef CONFIG_SCHED_HMP
 struct hmp_domain {
 	struct cpumask cpus;
+	struct cpumask possible_cpus;
 	struct list_head hmp_domains;
 };
 #endif /* CONFIG_SCHED_HMP */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3866dcc9972..10e7dbbbf83 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3381,10 +3381,10 @@ static int __init hmp_cpu_mask_setup(void)
 	dc = 0;
 	list_for_each(pos, &hmp_domains) {
 		domain = list_entry(pos, struct hmp_domain, hmp_domains);
-		cpulist_scnprintf(buf, 64, &domain->cpus);
+		cpulist_scnprintf(buf, 64, &domain->possible_cpus);
 		pr_debug("  HMP domain %d: %s\n", dc, buf);
 
-		for_each_cpu_mask(cpu, domain->cpus) {
+		for_each_cpu_mask(cpu, domain->possible_cpus) {
 			per_cpu(hmp_cpu_domain, cpu) = domain;
 		}
 		dc++;
@@ -3393,6 +3393,35 @@ static int __init hmp_cpu_mask_setup(void)
 	return 1;
 }
 
+static struct hmp_domain *hmp_get_hmp_domain_for_cpu(int cpu)
+{
+	struct hmp_domain *domain;
+	struct list_head *pos;
+
+	list_for_each(pos, &hmp_domains) {
+		domain = list_entry(pos, struct hmp_domain, hmp_domains);
+		if(cpumask_test_cpu(cpu, &domain->possible_cpus))
+			return domain;
+	}
+	return NULL;
+}
+
+static void hmp_online_cpu(int cpu)
+{
+	struct hmp_domain *domain = hmp_get_hmp_domain_for_cpu(cpu);
+
+	if(domain)
+		cpumask_set_cpu(cpu, &domain->cpus);
+}
+
+static void hmp_offline_cpu(int cpu)
+{
+	struct hmp_domain *domain = hmp_get_hmp_domain_for_cpu(cpu);
+
+	if(domain)
+		cpumask_clear_cpu(cpu, &domain->cpus);
+}
+
 /*
  * Migration thresholds should be in the range [0..1023]
  * hmp_up_threshold: min. load required for migrating tasks to a faster cpu
@@ -6190,11 +6219,17 @@ void trigger_load_balance(struct rq *rq, int cpu)
 
 static void rq_online_fair(struct rq *rq)
 {
+#ifdef CONFIG_SCHED_HMP
+	hmp_online_cpu(rq->cpu);
+#endif
 	update_sysctl();
 }
 
 static void rq_offline_fair(struct rq *rq)
 {
+#ifdef CONFIG_SCHED_HMP
+	hmp_offline_cpu(rq->cpu);
+#endif
 	update_sysctl();
 
 	/* Ensure any throttled groups are reachable by pick_next_task */