Michal Hocko [off-list ref] writes:

On Fri 16-03-12 23:09:24, Aneesh Kumar K.V wrote:
[...]

quoted

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6728a7a..4b36c5e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

[...]

quoted

@@ -4887,6 +5013,7 @@ err_cleanup:
 static struct cgroup_subsys_state * __ref
 mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 {
+	int idx;
 	struct mem_cgroup *memcg, *parent;
 	long error = -ENOMEM;
 	int node;

@@ -4929,9 +5056,14 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 		 * mem_cgroup(see mem_cgroup_put).
 		 */
 		mem_cgroup_get(parent);
+		for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
+			res_counter_init(&memcg->hugepage[idx],
+					 &parent->hugepage[idx]);

Hmm, I do not think we want to make groups deeper in the hierarchy
unlimited as we cannot reclaim. Shouldn't we copy the limit from the parent?
Still not ideal but slightly more expected behavior IMO.

But we should be limiting the child group based on parent's limit only
when hierarchy is set right ?

The hierarchy setups are still interesting and the limitations should be
described in the documentation...

It should behave similar to memcg. ie, if hierarchy is set, then we limit
using MIN(parent's limit, child's limit). May be I am missing some of
the details of memcg use_hierarchy config. My goal was to keep it
similar to memcg. Can you explain why do you think the patch would
make it any different ?

-aneesh