linux-kernel - [PATCH v2 5/5] sched/fair: cleanup for SIS

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Message-Id: <20220901131107.71785-5-wuyun.abel@bytedance.com>
Date:   Thu,  1 Sep 2022 21:11:07 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...e.de>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Josh Don <joshdon@...gle.com>, Chen Yu <yu.c.chen@...el.com>,
        Yicong Yang <yangyicong@...wei.com>,
        linux-kernel@...r.kernel.org, Abel Wu <wuyun.abel@...edance.com>
Subject: [PATCH v2 5/5] sched/fair: cleanup for SIS_PROP

The sched-domain of this cpu is only used when SIS_PROP is enabled,
and it should be irrelevant whether the local sd_llc is valid or
not, since all we care about is target sd_llc if !SIS_PROP.

Signed-off-by: Abel Wu <wuyun.abel@...edance.com>
---
 kernel/sched/fair.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 23b020c3d3a0..3561b18bfe9f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6399,16 +6399,16 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool
 	struct sched_domain *this_sd;
 	u64 time = 0;
 
-	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
-	if (!this_sd)
-		return -1;
-
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
 
 	if (sched_feat(SIS_PROP) && !has_idle_core) {
 		u64 avg_cost, avg_idle, span_avg;
 		unsigned long now = jiffies;
 
+		this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
+		if (!this_sd)
+			return -1;
+
 		/*
 		 * If we're busy, the assumption that the last idle period
 		 * predicts the future is flawed; age away the remaining
-- 
2.31.1