1 files changed, 33 insertions, 12 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 67c39642a512..a62098ec9deb 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2883,7 +2883,7 @@ void reweight_task(struct task_struct *p, int prio)
  *
  * hence icky!
  */
-static long calc_cfs_shares(struct cfs_rq *cfs_rq)
+static long calc_group_shares(struct cfs_rq *cfs_rq)
 {
 	long tg_weight, tg_shares, load, shares;
 	struct task_group *tg = cfs_rq->tg;
@@ -2920,6 +2920,36 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq)
 	 */
 	return clamp_t(long, shares, MIN_SHARES, tg_shares);
 }
+
+/*
+ * The runnable shares of this group are calculated as such
+ *
+ *          max(cfs_rq->avg.runnable_load_avg, cfs_rq->runnable_weight)
+ * shares * ------------------------------------------------------------
+ *               max(cfs_rq->avg.load_avg, cfs_rq->load.weight)
+ *
+ * We do this to keep the shares in line with expected load on the cfs_rq.
+ * Consider a cfs_rq that has several tasks wake up on this cfs_rq for the first
+ * time, it's runnable_load_avg is not going to be representative of the actual
+ * load this cfs_rq will now experience, which will bias us agaisnt this cfs_rq.
+ * The weight on the cfs_rq is the immediate effect of having new tasks
+ * enqueue'd onto it which should be used to calculate the new runnable shares.
+ * At the same time we need the actual load_avg to be the lower bounds for the
+ * calculation, to handle when our weight drops quickly from having entities
+ * dequeued.
+ */
+static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
+{
+	long load_avg = max(cfs_rq->avg.load_avg,
+			    scale_load_down(cfs_rq->load.weight));
+	long runnable = max(cfs_rq->avg.runnable_load_avg,
+			    scale_load_down(cfs_rq->runnable_weight));
+
+	runnable *= shares;
+	if (load_avg)
+		runnable /= load_avg;
+	return clamp_t(long, runnable, MIN_SHARES, shares);
+}
 # endif /* CONFIG_SMP */
 
 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
@@ -2945,17 +2975,8 @@ static void update_cfs_group(struct sched_entity *se)
 	if (likely(se->load.weight == shares))
 		return;
 #else
-	shares = calc_cfs_shares(gcfs_rq);
-	/*
-	 * The hierarchical runnable load metric is the proportional part
-	 * of this group's runnable_load_avg / load_avg.
-	 *
-	 * Note: we need to deal with very sporadic 'runnable > load' cases
-	 * due to numerical instability.
-	 */
-	runnable = shares * gcfs_rq->avg.runnable_load_avg;
-	if (runnable)
-		runnable /= max(gcfs_rq->avg.load_avg, gcfs_rq->avg.runnable_load_avg);
+	shares   = calc_group_shares(gcfs_rq);
+	runnable = calc_group_runnable(gcfs_rq, shares);
 #endif
 
 	reweight_entity(cfs_rq_of(se), se, shares, runnable);