linux-kernel - [PATCH v2] cpuset: Fix cpuset sched_relax_domain

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Date:	Fri, 30 Jan 2015 10:54:54 -0800
From:	Jason Low <jason.low2@...com>
To:	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	aswin@...com, scott.norton@...com, chegu_vinod@...com,
	Jason Low <jason.low2@...com>, stable@...r.kernel.org
Subject: [PATCH v2] cpuset: Fix cpuset sched_relax_domain_level

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>
---
 kernel/cpuset.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 64b257f..b589e57 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);
-- 
1.7.2.5



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