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From: Greg Thelen on 28 May 2010 11:30
Child groups should have a greater depth than their parents.
Prior to this change, the parent would incorrectly report zero
memory usage for child cgroups when use_hierarchy is enabled.

test script:
mount -t cgroup none /cgroups -o memory
cd /cgroups
mkdir cg1

echo 1 > cg1/memory.use_hierarchy
mkdir cg1/cg11

echo $$ > cg1/cg11/tasks
dd if=/dev/zero of=/tmp/foo bs=1M count=1

echo
echo CHILD
grep cache cg1/cg11/memory.stat

echo
echo PARENT
grep cache cg1/memory.stat

echo $$ > tasks
rmdir cg1/cg11 cg1
cd /
umount /cgroups

Using fae9c79, a recent patch that changed alloc_css_id() depth computation,
the parent incorrectly reports zero usage:
root(a)ubuntu:~# ./test
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0151844 s, 69.1 MB/s

CHILD
cache 1048576
total_cache 1048576

PARENT
cache 0
total_cache 0

With this patch, the parent correctly includes child usage:
root(a)ubuntu:~# ./test
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.0136827 s, 76.6 MB/s

CHILD
cache 1052672
total_cache 1052672

PARENT
cache 0
total_cache 1052672

Signed-off-by: Greg Thelen <gthelen(a)google.com>
---
kernel/cgroup.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 422cb19..3ac6f5b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4598,7 +4598,7 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
parent_css = parent->subsys[subsys_id];
child_css = child->subsys[subsys_id];
parent_id = parent_css->id;
- depth = parent_id->depth;
+ depth = parent_id->depth + 1;

child_id = get_new_cssid(ss, depth);
if (IS_ERR(child_id))
--
1.7.0.1

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