linux-kernel - Re: [PATCH v2] sched: Simplify __sched

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Date:   Mon, 24 Jan 2022 18:33:02 +0800
From:   Huichun Feng <foxhoundsk.tw@...il.com>
To:     henrybear327@...il.com
Cc:     bristot@...hat.com, bsegall@...gle.com, christian@...uner.io,
        dietmar.eggemann@....com, juri.lelli@...hat.com,
        linux-kernel@...r.kernel.org, mgorman@...e.de, mingo@...hat.com,
        peterz@...radead.org, rostedt@...dmis.org,
        vincent.guittot@...aro.org
Subject: Re: [PATCH v2] sched: Simplify __sched_init runtime checks

Improve runtime checks in __sched_init(void) by replacing if conditional
checks with preprocessor directives.

Signed-off-by: Chun-Hung Tseng <henrybear327@...il.com>
Signed-off-by: Huichun Feng <foxhoundsk.tw@...il.com>
---
 kernel/sched/core.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 848eaa0efe0e..1b27ca7f485a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9308,28 +9308,29 @@ void __init sched_init(void)
 #ifdef CONFIG_RT_GROUP_SCHED
 	ptr += 2 * nr_cpu_ids * sizeof(void **);
 #endif
-	if (ptr) {
-		ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
+
+#if defined(CONFIG_FAIR_GROUP_SCHED) || defined(CONFIG_RT_GROUP_SCHED)
+	ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-		root_task_group.se = (struct sched_entity **)ptr;
-		ptr += nr_cpu_ids * sizeof(void **);
+	root_task_group.se = (struct sched_entity **)ptr;
+	ptr += nr_cpu_ids * sizeof(void **);
 
-		root_task_group.cfs_rq = (struct cfs_rq **)ptr;
-		ptr += nr_cpu_ids * sizeof(void **);
+	root_task_group.cfs_rq = (struct cfs_rq **)ptr;
+	ptr += nr_cpu_ids * sizeof(void **);
 
-		root_task_group.shares = ROOT_TASK_GROUP_LOAD;
-		init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
+	root_task_group.shares = ROOT_TASK_GROUP_LOAD;
+	init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 #ifdef CONFIG_RT_GROUP_SCHED
-		root_task_group.rt_se = (struct sched_rt_entity **)ptr;
-		ptr += nr_cpu_ids * sizeof(void **);
-
-		root_task_group.rt_rq = (struct rt_rq **)ptr;
-		ptr += nr_cpu_ids * sizeof(void **);
+	root_task_group.rt_se = (struct sched_rt_entity **)ptr;
+	ptr += nr_cpu_ids * sizeof(void **);
 
+	root_task_group.rt_rq = (struct rt_rq **)ptr;
+	ptr += nr_cpu_ids * sizeof(void **);
 #endif /* CONFIG_RT_GROUP_SCHED */
-	}
+#endif /* CONFIG_FAIR_GROUP_SCHED || CONFIG_RT_GROUP_SCHED */
+
 #ifdef CONFIG_CPUMASK_OFFSTACK
 	for_each_possible_cpu(i) {
 		per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
-- 
2.34.1