[PATCH 3.16.y-ckt 107/165] cpuset: Fix cpuset sched_relax_domain_level

Luis Henriques luis.henriques at canonical.com
Wed Mar 25 14:01:20 UTC 2015

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.


From: Jason Low <jason.low2 at hp.com>

commit 283cb41f426b723a0255702b761b0fc5d1b53a81 upstream.

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()")
Signed-off-by: Jason Low <jason.low2 at hp.com>
Signed-off-by: Zefan Li <lizefan at huawei.com>
Signed-off-by: Tejun Heo <tj at kernel.org>
Tested-by: Serge Hallyn <serge.hallyn at canonical.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 kernel/cpuset.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 116a4164720a..524a8eef2965 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -503,9 +503,6 @@ static void update_domain_attr_tree(struct sched_domain_attr *dattr,
 	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);

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