From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Davydov Subject: Re: [patch 0/3] mm: memcontrol: eliminate charge reparenting Date: Sun, 21 Sep 2014 19:50:43 +0400 Message-ID: <20140921155043.GC32416@esperanza> References: <1411243235-24680-1-git-send-email-hannes@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <1411243235-24680-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: linux-mm@kvack.org, Michal Hocko , Greg Thelen , Tejun Heo , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org