[RFC v4 PATCH 4/7] sched: Unthrottle the throttled tasks

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

sched: Unthrottle the throttled tasks.

From: Bharata B Rao <bharata@linux.vnet.ibm.com>

Refresh runtimes when group's period expires. Unthrottle any
throttled groups at that time. Refreshing runtimes is driven through
a periodic timer.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
---
 kernel/sched.c      |    3 +++
 kernel/sched_fair.c |   51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 53 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 19069d3..dd56c72 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1886,6 +1886,8 @@ static inline u64 global_cfs_runtime(void)
 	return RUNTIME_INF;
 }
 
+void do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b);
+
 static inline void cfs_rq_runtime_lock(struct cfs_rq *cfs_rq)
 {
 	spin_lock(&cfs_rq->cfs_runtime_lock);
@@ -1905,6 +1907,7 @@ static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
 	struct cfs_bandwidth *cfs_b =
 		container_of(timer, struct cfs_bandwidth, cfs_period_timer);
 
+	do_sched_cfs_period_timer(cfs_b);
 	hrtimer_add_expires_ns(timer, ktime_to_ns(cfs_b->cfs_period));
 	return HRTIMER_RESTART;
 }
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ea7468c..3d0f006 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -191,6 +191,13 @@ find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 
 #ifdef CONFIG_CFS_HARD_LIMITS
 
+static inline
+struct cfs_rq *sched_cfs_period_cfs_rq(struct cfs_bandwidth *cfs_b, int cpu)
+{
+	return container_of(cfs_b, struct task_group,
+			cfs_bandwidth)->cfs_rq[cpu];
+}
+
 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
 {
 	return cfs_rq->cfs_throttled;
@@ -227,6 +234,49 @@ static inline void update_curr_group(struct sched_entity *curr,
 	sched_cfs_runtime_exceeded(curr, tsk_curr, delta_exec);
 }
 
+static void enqueue_entity_locked(struct cfs_rq *cfs_rq,
+		struct sched_entity *se, int wakeup);
+
+static void enqueue_throttled_entity(struct rq *rq, struct sched_entity *se)
+{
+	for_each_sched_entity(se) {
+		struct cfs_rq *gcfs_rq = group_cfs_rq(se);
+
+		if (se->on_rq || cfs_rq_throttled(gcfs_rq) ||
+				!gcfs_rq->nr_running)
+			break;
+		enqueue_entity_locked(cfs_rq_of(se), se, 0);
+	}
+}
+
+/*
+ * Refresh runtimes of all cfs_rqs in this group, i,e.,
+ * refresh runtimes of the representative cfs_rq of this
+ * tg on all cpus. Enqueue any throttled entity back.
+ */
+void do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b)
+{
+	int i;
+	const struct cpumask *span = sched_bw_period_mask();
+	unsigned long flags;
+
+	for_each_cpu(i, span) {
+		struct rq *rq = cpu_rq(i);
+		struct cfs_rq *cfs_rq = sched_cfs_period_cfs_rq(cfs_b, i);
+		struct sched_entity *se = cfs_rq->tg->se[i];
+
+		spin_lock_irqsave(&rq->lock, flags);
+		cfs_rq_runtime_lock(cfs_rq);
+		cfs_rq->cfs_time = 0;
+		if (cfs_rq_throttled(cfs_rq)) {
+			cfs_rq->cfs_throttled = 0;
+			enqueue_throttled_entity(rq, se);
+		}
+		cfs_rq_runtime_unlock(cfs_rq);
+		spin_unlock_irqrestore(&rq->lock, flags);
+	}
+}
+
 #else
 
 static inline void update_curr_group(struct sched_entity *curr,
@@ -310,7 +360,6 @@ find_matching_se(struct sched_entity **se, struct sched_entity **pse)
 
 #endif	/* CONFIG_FAIR_GROUP_SCHED */
 
-
 /**************************************************************
  * Scheduling class tree data structure manipulation methods:
  */