From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423290Ab2LGR1i (ORCPT ); Fri, 7 Dec 2012 12:27:38 -0500 Received: from cantor2.suse.de ([195.135.220.15]:36394 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755147Ab2LGR1h (ORCPT ); Fri, 7 Dec 2012 12:27:37 -0500 Date: Fri, 7 Dec 2012 18:27:34 +0100 From: Michal Hocko To: Ying Han Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, KAMEZAWA Hiroyuki , Johannes Weiner , Tejun Heo , Glauber Costa , Li Zefan Subject: Re: [patch v2 3/6] memcg: rework mem_cgroup_iter to use cgroup iterators Message-ID: <20121207172734.GG31938@dhcp22.suse.cz> References: <1353955671-14385-1-git-send-email-mhocko@suse.cz> <1353955671-14385-4-git-send-email-mhocko@suse.cz> <20121207085839.GB31938@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 07-12-12 09:12:25, Ying Han wrote: > On Fri, Dec 7, 2012 at 12:58 AM, Michal Hocko wrote: > > On Thu 06-12-12 19:43:52, Ying Han wrote: > > [...] > >> Forgot to mention, I was testing 3.7-rc6 with the two cgroup changes : > > > > Could you give a try to -mm tree as well. There are some changes for > > memcgs removal in that tree which are not in Linus's tree. > > I will give a try, which patchset you have in mind so i can double check? Have a look at ba5e0e6be1c76fd37508b2825372b28a90a5b729 in my tree. > I didn't find the place where the css pins the memcg, which either > something i missed or not in place in my tree. Yeah, it is carefully hidden ;). css pins cgroup (last css_put will call dput on the cgroup dentry - via css_dput_fn) and the last reference to memcg is dropped from ->destroy callback (mem_cgroup_destroy) called from cgroup_diput. > I twisted the patch a bit to make it closer to your v2 version, > but instead keep the mem_cgroup_put() as well as using > css_tryget(). Again, my test is happy with it: This is really strange, there must be something weird with ref counting going on. Anyway, thanks for your testing! I will try to enahance my testing some more next week. > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index f2eeee6..acec05a 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1004,6 +1004,7 @@ struct mem_cgroup *mem_cgroup_iter(struct > mem_cgroup *root, > if (prev && reclaim->generation != iter->generation) { > if (last_visited) { > css_put(&last_visited->css); > + mem_cgroup_put(last_visited); > iter->last_visited = NULL; > } > spin_unlock(&iter->iter_lock); > @@ -1041,15 +1042,22 @@ struct mem_cgroup *mem_cgroup_iter(struct > mem_cgroup *root, > if (reclaim) { > struct mem_cgroup *curr = memcg; > > - if (last_visited) > + if (last_visited) { > css_put(&last_visited->css); > + mem_cgroup_put(last_visited); > + } > > if (css && !memcg) > curr = container_of(css, struct > mem_cgroup, css); > > /* make sure that the cached memcg is not removed */ > - if (curr) > - css_get(&curr->css); > + if (curr) { > + mem_cgroup_get(curr); > + if (!css_tryget(&curr->css)) { > + mem_cgroup_put(curr); > + curr = NULL; > + } > + } > iter->last_visited = curr; > > if (!css) > > > --Ying > > > -- > > Michal Hocko > > SUSE Labs > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michal Hocko SUSE Labs