linux-kernel - [PATCH] sche/fair: static cpumasks for load balance

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Message-Id: <20220523094216.1746504-1-huangbing@kylinos.cn>
Date:   Mon, 23 May 2022 17:42:16 +0800
From:   Bing Huang <huangbing@...inos.cn>
To:     mingo@...hat.com
Cc:     peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, brauner@...nel.org,
        linux-kernel@...r.kernel.org, Bing Huang <huangbing@...inos.cn>
Subject: [PATCH] sche/fair: static cpumasks for load balance

The both cpu mask load_balance_mask and select_idle_mask just only used
in fair.c, but allocation in core.c in CONFIG_CPUMASK_OFFSTACK=y case,
and global via declare per cpu variations. More or less, it looks wired.

Signed-off-by: Bing Huang <huangbing@...inos.cn>
---
 kernel/sched/core.c  | 13 +++----------
 kernel/sched/fair.c  | 18 ++++++++++++++++--
 kernel/sched/sched.h |  4 ++++
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d58c0389eb23..64934c5e236d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9448,9 +9448,6 @@ LIST_HEAD(task_groups);
 static struct kmem_cache *task_group_cache __read_mostly;
 #endif
 
-DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
-DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
-
 void __init sched_init(void)
 {
 	unsigned long ptr = 0;
@@ -9494,14 +9491,10 @@ void __init sched_init(void)
 
 #endif /* CONFIG_RT_GROUP_SCHED */
 	}
+
 #ifdef CONFIG_CPUMASK_OFFSTACK
-	for_each_possible_cpu(i) {
-		per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
-			cpumask_size(), GFP_KERNEL, cpu_to_node(i));
-		per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
-			cpumask_size(), GFP_KERNEL, cpu_to_node(i));
-	}
-#endif /* CONFIG_CPUMASK_OFFSTACK */
+	init_working_cpumask();
+#endif
 
 	init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a68482d66535..3a4b0dd1beb5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5831,8 +5831,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 #ifdef CONFIG_SMP
 
 /* Working cpumask for: load_balance, load_balance_newidle. */
-DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
-DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
+static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
+static DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
 
 #ifdef CONFIG_NO_HZ_COMMON
 
@@ -7052,6 +7052,20 @@ balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 }
 #endif /* CONFIG_SMP */
 
+#ifdef CONFIG_CPUMASK_OFFSTACK
+void __init init_working_cpumask(void)
+{
+	int i;
+
+	for_each_possible_cpu(i) {
+		per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
+				cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+		per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
+				cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+	}
+}
+#endif
+
 static unsigned long wakeup_gran(struct sched_entity *se)
 {
 	unsigned long gran = sysctl_sched_wakeup_granularity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8dccb34eb190..9065be3def51 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3087,4 +3087,8 @@ extern int sched_dynamic_mode(const char *str);
 extern void sched_dynamic_update(int mode);
 #endif
 
+#ifdef CONFIG_CPUMASK_OFFSTACK
+extern void __init init_working_cpumask(void);
+#endif /* CONFIG_CPUMASK_OFFSTACK */
+
 #endif /* _KERNEL_SCHED_SCHED_H */
-- 
2.25.1


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