From 52ef2457bf5c6e9f6a3e3c2db216c39ddc83b553 Mon Sep 17 00:00:00 2001
From: Shrikanth Hegde <sshegde@linux.ibm.com>
Date: Tue, 26 Mar 2024 20:56:16 +0530
Subject: [PATCH] sched/fair: Combine EAS check with root_domain::overutilized
 access

References: bsc#1221157
Git-commit: 902e786c4a54a2c4f7462b9026bb56610888db3d
Patch-mainline: Queued in subsystem maintainer repository
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git

Access to root_domainoverutilized is always used with sched_energy_enabled in
the pattern:

  if (sched_energy_enabled && !overutilized)
         do something

So modify the helper function to utilize this pattern. This is more
readable code as it would say, do something when root domain is not
overutilized. This function always return true when EAS is disabled.

No change in functionality intended.

Suggested-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20240326152616.380999-1-sshegde@linux.ibm.com
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 kernel/sched/fair.c | 20 +++++++-------------
 1 file changed, 7 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 33ce8880e652..bd8d76258659 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6584,12 +6584,11 @@ static inline bool cpu_overutilized(int cpu)
 }
 
 /*
- * Ensure that caller can do EAS. overutilized value
- * make sense only if EAS is enabled
+ * overutilized value make sense only if EAS is enabled
  */
 static inline int is_rd_overutilized(struct root_domain *rd)
 {
-	return READ_ONCE(rd->overutilized);
+	return !sched_energy_enabled() || READ_ONCE(rd->overutilized);
 }
 
 static inline void set_rd_overutilized_status(struct root_domain *rd,
@@ -6608,8 +6607,6 @@ static inline void check_update_overutilized_status(struct rq *rq)
 	 * overutilized field is used for load balancing decisions only
 	 * if energy aware scheduler is being used
 	 */
-	if (!sched_energy_enabled())
-		return;
 
 	if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
 		set_rd_overutilized_status(rq->rd, SG_OVERUTILIZED);
@@ -7886,7 +7883,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
 
 	rcu_read_lock();
 	pd = rcu_dereference(rd->pd);
-	if (!pd || is_rd_overutilized(rd))
+	if (!pd)
 		goto unlock;
 
 	/*
@@ -8089,7 +8086,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 		    cpumask_test_cpu(cpu, p->cpus_ptr))
 			return cpu;
 
-		if (sched_energy_enabled()) {
+		if (!is_rd_overutilized(this_rq()->rd)) {
 			new_cpu = find_energy_efficient_cpu(p, prev_cpu);
 			if (new_cpu >= 0)
 				return new_cpu;
@@ -10900,12 +10897,9 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	if (busiest->group_type == group_misfit_task)
 		goto force_balance;
 
-	if (sched_energy_enabled()) {
-		struct root_domain *rd = env->dst_rq->rd;
-
-		if (rcu_dereference(rd->pd) && !is_rd_overutilized(rd))
-			goto out_balanced;
-	}
+	if (!is_rd_overutilized(env->dst_rq->rd) &&
+	    rcu_dereference(env->dst_rq->rd->pd))
+		goto out_balanced;
 
 	/* ASYM feature bypasses nice load balance check */
 	if (busiest->group_type == group_asym_packing)