Hi, I am sorry but I was quite busy at the time this has been discussed. Now that I got to this thread finally I am wondering whether this resp. other root cgroup exceptions have any follow up. I have seen the issue is fixed in Linus tree by 8de15e920dc8 ("mm: memcg: link page counters to root if use_hierarchy is false"). Thanks for taking care of that! I do agree that this approach is the most reasonable immediate fix. Btw. we have been carrying a warning about non hierarchical hierarchies for years in our distribution kernels and haven't heard of any actual bug reports (except for LTP driven ones). So we might be really close to simply drop this functionality completely. This would simplify the code and prevent from future surprises. Thanks! -- Michal Hocko SUSE Labs