[RFC PATCH 7/9 v4] Implement Workload Consolidation in idle_balance

[Yuyang Du <yuyang.du@intel.com>]

1) Skip pulling task to the idle non-consolidated CPUs.

2) In addition, for consolidated Idle CPU, we aggressively pull tasks from
   non-consolidated CPUs.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
---
 kernel/sched/fair.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 008cbc9..bf65fde 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2608,6 +2608,9 @@ static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
 static inline void update_cpu_concurrency(struct rq *rq);
 static struct sched_group *wc_find_group(struct sched_domain *sd,
 	struct task_struct *p, int this_cpu);
+static void wc_unload(struct cpumask *nonshielded, struct sched_domain *sd);
+static void wc_nonshielded_mask(int cpu, struct sched_domain *sd,
+	struct cpumask *mask);
 static int cpu_cc_capable(int cpu);
 
 /*
@@ -6808,6 +6811,22 @@ static int idle_balance(struct rq *this_rq)
 
 	update_blocked_averages(this_cpu);
 	rcu_read_lock();
+
+	sd = per_cpu(sd_wc, this_cpu);
+	if (sd) {
+		struct cpumask *nonshielded_cpus = __get_cpu_var(load_balance_mask);
+
+		cpumask_copy(nonshielded_cpus, cpu_active_mask);
+
+		/*
+		 * if we encounter shielded cpus here, don't do balance on them
+		 */
+		wc_nonshielded_mask(this_cpu, sd, nonshielded_cpus);
+		if (!cpumask_test_cpu(this_cpu, nonshielded_cpus))
+			goto unlock;
+		wc_unload(nonshielded_cpus, sd);
+	}
+
 	for_each_domain(this_cpu, sd) {
 		int continue_balancing = 1;
 		u64 t0, domain_cost;
@@ -6843,6 +6862,7 @@ static int idle_balance(struct rq *this_rq)
 		if (pulled_task || this_rq->nr_running > 0)
 			break;
 	}
+unlock:
 	rcu_read_unlock();
 
 	raw_spin_lock(&this_rq->lock);
-- 
1.7.9.5