linux-kernel - [PATCH 1/3] sched: don't repeat the initialization in sched

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Date:	Tue, 04 Jun 2013 14:23:12 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 1/3] sched: don't repeat the initialization in sched_init()

In sched_init(), there is no need to initialize 'root_task_group.shares' and
'root_task_group.cfs_bandwidth' repeatedly.

CC: Ingo Molnar <mingo@...nel.org>
CC: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
---
 kernel/sched/core.c |   46 +++++++++++++++++++++++++---------------------
 1 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 58453b8..c0c3716 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6955,6 +6955,31 @@ void __init sched_init(void)
 
 #endif /* CONFIG_CGROUP_SCHED */
 
+#ifdef CONFIG_FAIR_GROUP_SCHED
+	root_task_group.shares = ROOT_TASK_GROUP_LOAD;
+
+	/*
+	 * How much cpu bandwidth does root_task_group get?
+	 *
+	 * In case of task-groups formed thr' the cgroup filesystem, it
+	 * gets 100% of the cpu resources in the system. This overall
+	 * system cpu resource is divided among the tasks of
+	 * root_task_group and its child task-groups in a fair manner,
+	 * based on each entity's (task or task-group's) weight
+	 * (se->load.weight).
+	 *
+	 * In other words, if root_task_group has 10 tasks of weight
+	 * 1024) and two child groups A0 and A1 (of weight 1024 each),
+	 * then A0's share of the cpu resource is:
+	 *
+	 *	A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
+	 *
+	 * We achieve this by letting root_task_group's tasks sit
+	 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
+	 */
+	init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
+#endif
+
 	for_each_possible_cpu(i) {
 		struct rq *rq;
 
@@ -6966,28 +6991,7 @@ void __init sched_init(void)
 		init_cfs_rq(&rq->cfs);
 		init_rt_rq(&rq->rt, rq);
 #ifdef CONFIG_FAIR_GROUP_SCHED
-		root_task_group.shares = ROOT_TASK_GROUP_LOAD;
 		INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
-		/*
-		 * How much cpu bandwidth does root_task_group get?
-		 *
-		 * In case of task-groups formed thr' the cgroup filesystem, it
-		 * gets 100% of the cpu resources in the system. This overall
-		 * system cpu resource is divided among the tasks of
-		 * root_task_group and its child task-groups in a fair manner,
-		 * based on each entity's (task or task-group's) weight
-		 * (se->load.weight).
-		 *
-		 * In other words, if root_task_group has 10 tasks of weight
-		 * 1024) and two child groups A0 and A1 (of weight 1024 each),
-		 * then A0's share of the cpu resource is:
-		 *
-		 *	A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
-		 *
-		 * We achieve this by letting root_task_group's tasks sit
-		 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
-		 */
-		init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
 		init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
 #endif /* CONFIG_FAIR_GROUP_SCHED */
 
-- 
1.7.4.1

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