linux-kernel - Re: [PATCH 1/3] cpuset: initialize effective masks when clone

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Message-ID: <54DD6DA5.9030207@huawei.com>
Date:	Fri, 13 Feb 2015 11:21:09 +0800
From:	Zefan Li <lizefan@...wei.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Jason Low <jason.low2@...com>, LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH 1/3] cpuset: initialize effective masks when clone_children
 is enabled

From: Jason Low <jason.low2@...com>

The cpuset.sched_relax_domain_level can control how far we do
immediate load balancing on a system. However, it was found on recent
kernels that echo'ing a value into cpuset.sched_relax_domain_level
did not reduce any immediate load balancing.

The reason this occurred was because the update_domain_attr_tree() traversal
did not update for the "top_cpuset". This resulted in nothing being changed
when modifying the sched_relax_domain_level parameter.

This patch is able to address that problem by having update_domain_attr_tree()
allow updates for the root in the cpuset traversal.

Fixes: fc560a26acce ("cpuset: replace cpuset->stack_list with cpuset_for_each_descendant_pre()")
Cc: <stable@...r.kernel.org> # 3.9+
Signed-off-by: Jason Low <jason.low2@...com>
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 kernel/cpuset.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 29463c2..9e25599 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -548,9 +548,6 @@ static void update_domain_attr_tree(struct sched_domain_attr *dattr,
 
 	rcu_read_lock();
 	cpuset_for_each_descendant_pre(cp, pos_css, root_cs) {
-		if (cp == root_cs)
-			continue;
-
 		/* skip the whole subtree if @cp doesn't have any CPU */
 		if (cpumask_empty(cp->cpus_allowed)) {
 			pos_css = css_rightmost_descendant(pos_css);
-- 
1.8.0.2

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