linux-kernel - [PATCH 10/13] hperf_hmp: idle pull function.

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Date:	Fri, 06 Nov 2015 15:02:44 +0300
From:	Arseniy Krasnov <a.krasnov@...sung.com>
To:	linux@....linux.org.uk, mingo@...hat.com, peterz@...radead.org
Cc:	a.krasnov@...sung.com, v.tyrtov@...sung.com,
	s.rogachev@...sung.com, linux-kernel@...r.kernel.org,
	Tarek Dakhran <t.dakhran@...sung.com>,
	Sergey Dyasly <s.dyasly@...sung.com>,
	Dmitriy Safonov <d.safonov@...tner.samsung.com>,
	Ilya Maximets <i.maximets@...sung.com>
Subject: [PATCH 10/13] hperf_hmp: idle pull function.

	HMP idle pull is triggered when CPU becomes idle. It tries to pull task
from another cluster when it is overloaded. Also A7 can't pull alone task from
A15, but A15 can do that with A7 core. Task for migration is chosen in the same
way as for other HMP migration cases - using 'druntime' metric. Only difference
is that migration task doesn't need to run 5ms on its cluster before migration.

Signed-off-by: Tarek Dakhran <t.dakhran@...sung.com>
Signed-off-by: Sergey Dyasly <s.dyasly@...sung.com>
Signed-off-by: Dmitriy Safonov <d.safonov@...tner.samsung.com>
Signed-off-by: Arseniy Krasnov <a.krasnov@...sung.com>
Signed-off-by: Ilya Maximets <i.maximets@...sung.com>
---
 kernel/sched/fair.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4fda1ec..fd16729 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7421,6 +7421,72 @@ static unsigned int try_to_move_task(struct task_struct *migrate_task,
 }
 
 /**
+ * hmp_idle_pull(): Pulls task from opposite domain of this_cpu to this_cpu.
+ * @sd: Current sched domain.
+ * @this_cpu: without NO_HZ same as smp_processor_id().
+ *
+ * Returns moved weight.
+ *
+ * Chooses task by its druntime. Ignores task's druntime and
+ * time of last HMP migration. Also A7 can't pulls task from A15
+ * if A15 become idle.
+ */
+static unsigned int hmp_idle_pull(struct sched_domain *sd, int this_cpu)
+{
+	unsigned int ld_moved = 0;
+	struct task_struct *task_to_pull;
+	unsigned long local_flags;
+	int idle_stopper = 0;
+	struct rq *local_rq;
+	struct rq *rq;
+
+	local_irq_save(local_flags);
+	local_rq = cpu_rq(this_cpu);
+	rq = get_unfair_rq(sd, this_cpu);
+
+	if (!rq) {
+		local_irq_restore(local_flags);
+		return 0;
+	}
+	double_lock_balance(rq, local_rq);
+
+	if (rq->active_balance)
+		goto unlock;
+
+	if (local_rq->active_balance)
+		goto unlock;
+
+	/* Forbids secondary CPUs to pull alone task from primary CPUs */
+	if (!cpu_is_fastest(this_cpu) && rq->cfs.h_nr_running <= 1)
+		goto unlock;
+
+	/* Get task to pull from opposite domain to this_cpu */
+	task_to_pull = get_migration_candidate(sd, rq, 1, this_cpu);
+
+	if (!task_to_pull)
+		goto unlock;
+
+	ld_moved = try_to_move_task(task_to_pull, this_cpu, &idle_stopper);
+
+	if (idle_stopper) {
+		rq->push_cpu = this_cpu;
+		rq->active_balance = 1;
+		rq->migrate_task = task_to_pull;
+	}
+
+unlock:
+	double_rq_unlock(local_rq, rq);
+	local_irq_restore(local_flags);
+
+	if (idle_stopper)
+		stop_one_cpu_nowait(rq->cpu, active_load_balance_cpu_stop,
+				    rq, &rq->active_balance_work);
+
+	return ld_moved;
+}
+
+
+/**
  * swap_tasks(): swaps two tasks from different HMP domains
  * @sd: Current sched domain
  * @this_cpu: without NO_HZ same as smp_processor_id().
-- 
1.9.1

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