With EAS, a group should be set overloaded if at least 1 CPU in the group
is overutilized but it can happen that a CPU is fully utilized by tasks
because of clamping the compute capacity of the CPU. In such case, the CPU
is not overutilized and as a result should not be set overloaded as well.

group_overloaded being a higher priority than group_misfit, such group can
be selected as the busiest group instead of a group with a mistfit task
and prevents load_balance to select the CPU with the misfit task to pull
the latter on a fitting CPU.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Pierre Gondois <pierre.gondois@arm.com>
---
 kernel/sched/fair.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1855975b8248..b10f04715251 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9987,6 +9987,7 @@ struct sg_lb_stats {
 	unsigned int group_asym_packing;	/* Tasks should be moved to preferred CPU */
 	unsigned int group_smt_balance;		/* Task on busy SMT be moved */
 	unsigned long group_misfit_task_load;	/* A CPU has a task too big for its capacity */
+	unsigned int group_overutilized;	/* At least one CPU is overutilized in the group */
 #ifdef CONFIG_NUMA_BALANCING
 	unsigned int nr_numa_running;
 	unsigned int nr_preferred_running;
@@ -10219,6 +10220,13 @@ group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 static inline bool
 group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 {
+	/*
+	 * With EAS and uclamp, 1 CPU in the group must be overutilized to
+	 * consider the group overloaded.
+	 */
+	if (sched_energy_enabled() && !sgs->group_overutilized)
+		return false;
+
 	if (sgs->sum_nr_running <= sgs->group_weight)
 		return false;
 
@@ -10402,14 +10410,12 @@ sched_reduced_capacity(struct rq *rq, struct sched_domain *sd)
  * @group: sched_group whose statistics are to be updated.
  * @sgs: variable to hold the statistics for this group.
  * @sg_overloaded: sched_group is overloaded
- * @sg_overutilized: sched_group is overutilized
  */
 static inline void update_sg_lb_stats(struct lb_env *env,
 				      struct sd_lb_stats *sds,
 				      struct sched_group *group,
 				      struct sg_lb_stats *sgs,
-				      bool *sg_overloaded,
-				      bool *sg_overutilized)
+				      bool *sg_overloaded)
 {
 	int i, nr_running, local_group, sd_flags = env->sd->flags;
 	bool balancing_at_rd = !env->sd->parent;
@@ -10431,7 +10437,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
 		sgs->sum_nr_running += nr_running;
 
 		if (cpu_overutilized(i))
-			*sg_overutilized = 1;
+			sgs->group_overutilized = 1;
 
 		/*
 		 * No need to call idle_cpu() if nr_running is not 0
@@ -11103,13 +11109,15 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 				update_group_capacity(env->sd, env->dst_cpu);
 		}
 
-		update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded, &sg_overutilized);
+		update_sg_lb_stats(env, sds, sg, sgs, &sg_overloaded);
 
 		if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
 			sds->busiest = sg;
 			sds->busiest_stat = *sgs;
 		}
 
+		sg_overutilized |= sgs->group_overutilized;
+
 		/* Now, start updating sd_lb_stats */
 		sds->total_load += sgs->group_load;
 		sds->total_capacity += sgs->group_capacity;
-- 
2.43.0