Okay, so after recent discussions, I am proposing the following
patch. It won't remove hierarchy, or anything like that. Just default
to true in the root cgroup, and print a warning once if you try
to set it back to 0.
I am not adding it to feature-removal-schedule.txt because I don't
view it as a consensus. Rather, changing the default would allow us
to give it a time around in the open, and see if people complain
and what we can learn about that.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Tejun Heo <tj@xxxxxxxxxx>
---
mm/memcontrol.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 85f7790..c37e4c1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3993,6 +3993,10 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
if (memcg->use_hierarchy == val)
goto out;
+ WARN_ONCE(!parent_memcg && memcg->use_hierarchy,
+ "Non-hierarchical memcg is considered for deprecation\n"
+ "Please consider reorganizing your tree to work with hierarchical accounting\n"
+ "If you have any reason not to, let us know at cgroups@xxxxxxxxxxxxxxx\n");
/*
* If parent's use_hierarchy is set, we can't make any modifications
* in the child subtrees. If it is unset, then the change can
@@ -5221,6 +5225,7 @@ mem_cgroup_create(struct cgroup *cont)
INIT_WORK(&stock->work, drain_local_stock);
}
hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
+ memcg->use_hierarchy = true;
} else {
parent = mem_cgroup_from_cont(cont->parent);
memcg->use_hierarchy = parent->use_hierarchy;
--
1.7.10.2
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