Hi Johannes, On Sat, Sep 20, 2014 at 04:00:32PM -0400, Johannes Weiner wrote: > The decoupling of css from the user-visible cgroup, word-sized per-cpu > css reference counters, and css iterators that include offlined groups > means we can take per-charge css references, continue to reclaim from > offlined groups, and so get rid of the error-prone charge reparenting. I haven't reviewed this set yet, but I agree that zapping user memory reparenting sounds like a sane idea, because reparenting won't let the css go in most cases anyway due to swap and kmem charges. However, I think we must reparent list_lru items, otherwise per-memcg arrays (kmem_caches, list_lrus) will grow uncontrollably due to dead css's, which is unacceptable. Note it isn't the same as the user memory reparenting, because we don't need to reparent kmem_cache objects or charges - they can stay where they are pinning the css till they are freed, because the memcg_cache_id, which I want to free on offline, is not used for kmem allocations/frees after css offline. Actually we only need to empty the list_lru corresponding to the dead memory cgroup, which is relatively easy to implement. This is what patch 13 of the "Per memcg slab shrinkers" patch set, which I sent recently, does (see https://lkml.org/lkml/2014/9/21/64). What do you think about it? Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>