linux-kernel - [RFC PATCH 16/16 v3] Intercept periodic load balancing

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Message-Id: <1401431772-14320-17-git-send-email-yuyang.du@intel.com>
Date:	Fri, 30 May 2014 14:36:12 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	mingo@...hat.com, peterz@...radead.org, rafael.j.wysocki@...el.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Cc:	arjan.van.de.ven@...el.com, len.brown@...el.com,
	alan.cox@...el.com, mark.gross@...el.com, pjt@...gle.com,
	bsegall@...gle.com, morten.rasmussen@....com,
	vincent.guittot@...aro.org, rajeev.d.muralidhar@...el.com,
	vishwesh.m.rudramuni@...el.com, nicole.chalhoub@...el.com,
	ajaya.durg@...el.com, harinarayanan.seshadri@...el.com,
	jacob.jun.pan@...ux.intel.com, fengguang.wu@...el.com,
	yuyang.du@...el.com
Subject: [RFC PATCH 16/16 v3] Intercept periodic load balancing

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

In periodic load balancing, we do two things:

1) Skip pulling task to the 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@...el.com>
---
 kernel/sched/fair.c |   51 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1b8dd45..d22ac87 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7260,17 +7260,54 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle, struc
 static void run_rebalance_domains(struct softirq_action *h)
 {
 	struct rq *this_rq = this_rq();
+	int this_cpu = cpu_of(this_rq);
+	struct sched_domain *sd;
 	enum cpu_idle_type idle = this_rq->idle_balance ?
 						CPU_IDLE : CPU_NOT_IDLE;
 
-	rebalance_domains(this_rq, idle);
+	rcu_read_lock();
+	sd = top_flag_domain(this_cpu, SD_WORKLOAD_CONSOLIDATION);
+	if (sd) {
+		struct cpumask *nonshielded_cpus = __get_cpu_var(load_balance_mask);
 
-	/*
-	 * If this cpu has a pending nohz_balance_kick, then do the
-	 * balancing on behalf of the other idle cpus whose ticks are
-	 * stopped.
-	 */
-	nohz_idle_balance(this_rq, idle);
+		/*
+		 * if we encounter shielded cpus here, don't do balance on them
+		 */
+		cpumask_copy(nonshielded_cpus, cpu_active_mask);
+
+		wc_nonshielded_mask(this_cpu, sd, nonshielded_cpus);
+
+		/*
+		 * aggressively unload the shielded cpus to unshielded cpus
+		 */
+		wc_unload(nonshielded_cpus, sd);
+		rcu_read_unlock();
+
+		if (cpumask_test_cpu(this_cpu, nonshielded_cpus)) {
+			struct cpumask *idle_cpus = __get_cpu_var(local_cpu_mask);
+			cpumask_and(idle_cpus, nonshielded_cpus, nohz.idle_cpus_mask);
+
+			rebalance_domains(this_rq, idle);
+
+			/*
+			 * If this cpu has a pending nohz_balance_kick, then do the
+			 * balancing on behalf of the other idle cpus whose ticks are
+			 * stopped.
+			 */
+			nohz_idle_balance(this_rq, idle, idle_cpus);
+		}
+	}
+	else {
+		rcu_read_unlock();
+		rebalance_domains(this_rq, idle);
+
+		/*
+		 * If this cpu has a pending nohz_balance_kick, then do the
+		 * balancing on behalf of the other idle cpus whose ticks are
+		 * stopped.
+		 */
+		nohz_idle_balance(this_rq, idle, nohz.idle_cpus_mask);
+	}
 }
 
 /*
-- 
1.7.9.5

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