Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286Ab3DGGBL (ORCPT ); Sun, 7 Apr 2013 02:01:11 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:16153 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750928Ab3DGGBJ (ORCPT ); Sun, 7 Apr 2013 02:01:09 -0400 Message-ID: <51610B78.7080001@huawei.com> Date: Sun, 7 Apr 2013 14:00:24 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Michal Hocko CC: , LKML , Cgroups , Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner Subject: Re: [RFC][PATCH 0/7] memcg: make memcg's life cycle the same as cgroup References: <515BF233.6070308@huawei.com> <20130404120049.GI29911@dhcp22.suse.cz> In-Reply-To: <20130404120049.GI29911@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2042 Lines: 45 On 2013/4/4 20:00, Michal Hocko wrote: > On Wed 03-04-13 17:11:15, Li Zefan wrote: >> (I'll be off from my office soon, and I won't be responsive in the following >> 3 days.) >> >> I'm working on converting memcg to use cgroup->id, and then we can kill css_id. >> >> Now memcg has its own refcnt, so when a cgroup is destroyed, the memcg can >> still be alive. This patchset converts memcg to always use css_get/put, so >> memcg will have the same life cycle as its corresponding cgroup, and then >> it's always safe for memcg to use cgroup->id. >> >> The historical reason that memcg didn't use css_get in some cases, is that >> cgroup couldn't be removed if there're still css refs. The situation has >> changed so that rmdir a cgroup will succeed regardless css refs, but won't >> be freed until css refs goes down to 0. >> >> This is an early post, and it's NOT TESTED. I just want to see if the changes >> are fine in general. > > yes, I like the approach and it looks correct as well (some minor things > mentioned in the patches). Thanks a lot Li! This will make our lifes much > easier. The separate ref counting was PITA especially after > introduction of kmem accounting which made its usage even more trickier. > >> btw, after this patchset I think we don't need to free memcg via RCU, because >> cgroup is already freed in RCU callback. > > But this depends on changes waiting in for-3.10 branch, right? What changes? memcg changes or cgroup core changes? I don't think this depends on anything in cgroup 3.10 branch. > Anyway, I think we should be safe with the workqueue based releasing as > well once mem_cgroup_{get,put} are gone, right? > cgroup calls mem_cgroup_css_free() in a work function, so seems memcg doesn't need to use RCU or workqueue in mem_cgroup_css_free(). -- 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/