From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH v3 3/6] memcg: Simplify mem_cgroup_force_empty_list error handling Date: Mon, 29 Oct 2012 17:58:45 +0400 Message-ID: <508E8B95.406@parallels.com> References: <1351251453-6140-1-git-send-email-mhocko@suse.cz> <1351251453-6140-4-git-send-email-mhocko@suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1351251453-6140-4-git-send-email-mhocko-AlSwsSmVLrQ@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andrew Morton , Tejun Heo , Li Zefan , Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh > > Changes since v1 > - use kerndoc > - be more specific about mem_cgroup_move_parent possible failures > > Signed-off-by: Michal Hocko > Reviewed-by: Tejun Heo Reviewed-by: Glauber Costa > + * move charges to its parent or the root cgroup if the group has no > + * parent (aka use_hierarchy==0). > + * Although this might fail (get_page_unless_zero, isolate_lru_page or > + * mem_cgroup_move_account fails) the failure is always temporary and > + * it signals a race with a page removal/uncharge or migration. In the > + * first case the page is on the way out and it will vanish from the LRU > + * on the next attempt and the call should be retried later. > + * Isolation from the LRU fails only if page has been isolated from > + * the LRU since we looked at it and that usually means either global > + * reclaim or migration going on. The page will either get back to the > + * LRU or vanish. I just wonder for how long can it go in the worst case?