1 files changed, 39 insertions, 14 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7522816cd7f6..410d78df23e4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -692,8 +692,6 @@ int tg_nop(struct task_group *tg, void *data)
 }
 #endif
 
-void update_cpu_load(struct rq *this_rq);
-
 static void set_load_weight(struct task_struct *p)
 {
 	int prio = p->static_prio - MAX_RT_PRIO;
@@ -2620,22 +2618,13 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
  * scheduler tick (TICK_NSEC). With tickless idle this will not be called
  * every tick. We fix it up based on jiffies.
  */
-void update_cpu_load(struct rq *this_rq)
+static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
+			      unsigned long pending_updates)
 {
-	unsigned long this_load = this_rq->load.weight;
-	unsigned long curr_jiffies = jiffies;
-	unsigned long pending_updates;
 	int i, scale;
 
 	this_rq->nr_load_updates++;
 
-	/* Avoid repeated calls on same jiffy, when moving in and out of idle */
-	if (curr_jiffies == this_rq->last_load_update_tick)
-		return;
-
-	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
-	this_rq->last_load_update_tick = curr_jiffies;
-
 	/* Update our load: */
 	this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
 	for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
@@ -2660,9 +2649,45 @@ void update_cpu_load(struct rq *this_rq)
 	sched_avg_update(this_rq);
 }
 
+/*
+ * Called from nohz_idle_balance() to update the load ratings before doing the
+ * idle balance.
+ */
+void update_idle_cpu_load(struct rq *this_rq)
+{
+	unsigned long curr_jiffies = jiffies;
+	unsigned long load = this_rq->load.weight;
+	unsigned long pending_updates;
+
+	/*
+	 * Bloody broken means of dealing with nohz, but better than nothing..
+	 * jiffies is updated by one cpu, another cpu can drift wrt the jiffy
+	 * update and see 0 difference the one time and 2 the next, even though
+	 * we ticked at roughtly the same rate.
+	 *
+	 * Hence we only use this from nohz_idle_balance() and skip this
+	 * nonsense when called from the scheduler_tick() since that's
+	 * guaranteed a stable rate.
+	 */
+	if (load || curr_jiffies == this_rq->last_load_update_tick)
+		return;
+
+	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
+	this_rq->last_load_update_tick = curr_jiffies;
+
+	__update_cpu_load(this_rq, load, pending_updates);
+}
+
+/*
+ * Called from scheduler_tick()
+ */
 static void update_cpu_load_active(struct rq *this_rq)
 {
-	update_cpu_load(this_rq);
+	/*
+	 * See the mess in update_idle_cpu_load().
+	 */
+	this_rq->last_load_update_tick = jiffies;
+	__update_cpu_load(this_rq, this_rq->load.weight, 1);
 
 	calc_load_account_active(this_rq);
 }