[RFC PATCH 14/16 v3] Intercept idle balancing

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

We intercept load balancing to contain the load and load balancing in
the consolidated CPUs according to our consolidating mechanism.

In idle balancing, we do two things:

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 |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1c9ac08..220773f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6692,6 +6692,22 @@ static int idle_balance(struct rq *this_rq)
 
 	update_blocked_averages(this_cpu);
 	rcu_read_lock();
+
+	sd = top_flag_domain(this_cpu, SD_WORKLOAD_CONSOLIDATION);
+	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) {
 		unsigned long interval;
 		int continue_balancing = 1;
@@ -6724,6 +6740,7 @@ static int idle_balance(struct rq *this_rq)
 		if (pulled_task)
 			break;
 	}
+unlock:
 	rcu_read_unlock();
 
 	raw_spin_lock(&this_rq->lock);
-- 
1.7.9.5