[RFC PATCH 1/4] sched/fair: Extract the function to get the sd_llc_shared

[Chen Yu]

Introduce get_llc_shared() to get the sd_llc_shared of dst_cpu, if
the current domain is in LLC. Let SIS_UTIL be the first user to use
this function. Prepare for later use by ILB_UTIL.

No functional change is intended.

Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
---
 kernel/sched/fair.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6189d1a45635..b3a24aead848 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10043,10 +10043,21 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
 	return idlest;
 }
 
+/* Get the LLC shared information of dst CPU if doing balance in LLC */
+static struct sched_domain_shared *get_llc_shared(struct lb_env *env)
+{
+	struct sched_domain_shared *sd_share = NULL;
+
+	if (per_cpu(sd_llc_size, env->dst_cpu) == env->sd->span_weight)
+		sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
+
+	return sd_share;
+}
+
 static void update_idle_cpu_scan(struct lb_env *env,
-				 unsigned long sum_util)
+				 unsigned long sum_util,
+				 struct sched_domain_shared *sd_share)
 {
-	struct sched_domain_shared *sd_share;
 	int llc_weight, pct;
 	u64 x, y, tmp;
 	/*
@@ -10060,14 +10071,11 @@ static void update_idle_cpu_scan(struct lb_env *env,
 	if (!sched_feat(SIS_UTIL) || env->idle == CPU_NEWLY_IDLE)
 		return;
 
-	llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
-	if (env->sd->span_weight != llc_weight)
-		return;
-
-	sd_share = rcu_dereference(per_cpu(sd_llc_shared, env->dst_cpu));
 	if (!sd_share)
 		return;
 
+	llc_weight = per_cpu(sd_llc_size, env->dst_cpu);
+
 	/*
 	 * The number of CPUs to search drops as sum_util increases, when
 	 * sum_util hits 85% or above, the scan stops.
@@ -10122,6 +10130,7 @@ static void update_idle_cpu_scan(struct lb_env *env,
 
 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
 {
+	struct sched_domain_shared *sd_share = get_llc_shared(env);
 	struct sched_group *sg = env->sd->groups;
 	struct sg_lb_stats *local = &sds->local_stat;
 	struct sg_lb_stats tmp_sgs;
@@ -10190,7 +10199,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
 		trace_sched_overutilized_tp(rd, SG_OVERUTILIZED);
 	}
 
-	update_idle_cpu_scan(env, sum_util);
+	update_idle_cpu_scan(env, sum_util, sd_share);
 }
 
 /**
-- 
2.25.1