Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758362Ab1FVSdf (ORCPT ); Wed, 22 Jun 2011 14:33:35 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55694 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757942Ab1FVSde (ORCPT ); Wed, 22 Jun 2011 14:33:34 -0400 Date: Wed, 22 Jun 2011 20:33:31 +0200 From: Michal Hocko To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" , "bsingharora@gmail.com" , Ying Han , "hannes@cmpxchg.org" Subject: Re: [PATCH 1/7] Fix mem_cgroup_hierarchical_reclaim() to do stable hierarchy walk. Message-ID: <20110622183249.GA27191@tiehlicka.suse.cz> References: <20110616124730.d6960b8b.kamezawa.hiroyu@jp.fujitsu.com> <20110616125141.5fbd230f.kamezawa.hiroyu@jp.fujitsu.com> <20110622151500.GF14343@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110622151500.GF14343@tiehlicka.suse.cz> 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 Content-Length: 2375 Lines: 72 On Wed 22-06-11 17:15:00, Michal Hocko wrote: > On Thu 16-06-11 12:51:41, KAMEZAWA Hiroyuki wrote: > [...] > > @@ -1667,41 +1668,28 @@ static int mem_cgroup_hierarchical_recla > > if (!check_soft && root_mem->memsw_is_minimum) > > noswap = true; > > > > - while (1) { > > +again: > > + if (!shrink) { > > + visit = 0; > > + for_each_mem_cgroup_tree(victim, root_mem) > > + visit++; > > + } else { > > + /* > > + * At shrinking, we check the usage again in caller side. > > + * so, visit children one by one. > > + */ > > + visit = 1; > > + } > > + /* > > + * We are not draining per cpu cached charges during soft limit reclaim > > + * because global reclaim doesn't care about charges. It tries to free > > + * some memory and charges will not give any. > > + */ > > + if (!check_soft) > > + drain_all_stock_async(root_mem); > > + > > + while (visit--) { > > This is racy, isn't it? What prevents some groups to disapear in the > meantime? We would reclaim from those that are left more that we want. > > Why cannot we simply do something like (totally untested): > > Index: linus_tree/mm/memcontrol.c > =================================================================== > --- linus_tree.orig/mm/memcontrol.c 2011-06-22 17:11:54.000000000 +0200 > +++ linus_tree/mm/memcontrol.c 2011-06-22 17:13:05.000000000 +0200 > @@ -1652,7 +1652,7 @@ static int mem_cgroup_hierarchical_recla > unsigned long reclaim_options, > unsigned long *total_scanned) > { > - struct mem_cgroup *victim; > + struct mem_cgroup *victim, *first_victim = NULL; > int ret, total = 0; > int loop = 0; > bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP; > @@ -1669,6 +1669,11 @@ static int mem_cgroup_hierarchical_recla > > while (1) { > victim = mem_cgroup_select_victim(root_mem); > + if (!first_victim) > + first_victim = victim; > + else if (first_victim == victim) > + break; this will obviously need css_get and css_put to make sure that the group doesn't disappear in the meantime. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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/