From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751427AbaIUPu4 (ORCPT ); Sun, 21 Sep 2014 11:50:56 -0400 Received: from mx2.parallels.com ([199.115.105.18]:59172 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751324AbaIUPuy (ORCPT ); Sun, 21 Sep 2014 11:50:54 -0400 Date: Sun, 21 Sep 2014 19:50:43 +0400 From: Vladimir Davydov To: Johannes Weiner CC: , Michal Hocko , Greg Thelen , Tejun Heo , , Subject: Re: [patch 0/3] mm: memcontrol: eliminate charge reparenting 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" Content-Disposition: inline In-Reply-To: <1411243235-24680-1-git-send-email-hannes@cmpxchg.org> X-Originating-IP: [81.5.99.36] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: 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