linux-kernel - [PATCH v2 2/2] sched/fair: Use helper function to access rd->overutilized

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Message-Id: <20240228071621.602596-3-sshegde@linux.ibm.com>
Date: Wed, 28 Feb 2024 12:46:21 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org
Cc: sshegde@...ux.ibm.com, yu.c.chen@...el.com, dietmar.eggemann@....com,
        linux-kernel@...r.kernel.org, nysal@...ux.ibm.com,
        aboorvad@...ux.ibm.com, srikar@...ux.vnet.ibm.com, vschneid@...hat.com,
        pierre.gondois@....com, morten.rasmussen@....com, qyousef@...alina.io
Subject: [PATCH v2 2/2] sched/fair: Use helper function to access rd->overutilized

Overutilized field is accessed directly in multiple places.
So it could use a helper function. That way one might be more
informed that it needs to be used only in case of EAS.

No change in functionality intended.

Signed-off-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
---
 kernel/sched/fair.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3105fb08b87e..c085fe8421b8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6670,6 +6670,15 @@ static inline bool cpu_overutilized(int cpu)
 	return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
 }

+/*
+ * Ensure that caller can do EAS. overutilized value
+ * make sense only if EAS is enabled
+ */
+static inline int is_rd_overutilized(struct root_domain *rd)
+{
+	return READ_ONCE(rd->overutilized);
+}
+
 static inline void update_rd_overutilized_status(struct root_domain *rd,
 						 int status)
 {
@@ -6686,7 +6695,7 @@ static inline void check_update_overutilized_status(struct rq *rq)
 	 * if energy aware scheduler is being used
 	 */
 	if (sched_energy_enabled()) {
-		if (!READ_ONCE(rq->rd->overutilized) && cpu_overutilized(rq->cpu))
+		if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu))
 			update_rd_overutilized_status(rq->rd, SG_OVERUTILIZED);
 	}
 }
@@ -6694,6 +6703,7 @@ static inline void check_update_overutilized_status(struct rq *rq)
 static inline void check_update_overutilized_status(struct rq *rq) { }
 static inline void update_rd_overutilized_status(struct root_domain *rd,
 						 bool status) { }
+static inline int is_rd_overutilized(struct root_domain *rd) { }
 #endif

 /* Runqueue only has SCHED_IDLE tasks enqueued */
@@ -7969,7 +7979,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)

 	rcu_read_lock();
 	pd = rcu_dereference(rd->pd);
-	if (!pd || READ_ONCE(rd->overutilized))
+	if (!pd || is_rd_overutilized(rd))
 		goto unlock;

 	/*
@@ -10872,7 +10882,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
 	if (sched_energy_enabled()) {
 		struct root_domain *rd = env->dst_rq->rd;

-		if (rcu_dereference(rd->pd) && !READ_ONCE(rd->overutilized))
+		if (rcu_dereference(rd->pd) && !is_rd_overutilized(rd))
 			goto out_balanced;
 	}

--
2.39.3