Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756197AbZAIEsw (ORCPT ); Thu, 8 Jan 2009 23:48:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753307AbZAIEso (ORCPT ); Thu, 8 Jan 2009 23:48:44 -0500 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:56545 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753254AbZAIEsn (ORCPT ); Thu, 8 Jan 2009 23:48:43 -0500 Date: Fri, 9 Jan 2009 13:47:36 +0900 From: KAMEZAWA Hiroyuki To: balbir@linux.vnet.ibm.com Cc: Daisuke Nishimura , linux-mm@kvack.org, linux-kernel@vger.kernel.org, lizf@cn.fujitsu.com, menage@google.com, "kosaki.motohiro@jp.fujitsu.com" Subject: Re: [RFC][PATCH 1/4] memcg: fix for mem_cgroup_get_reclaim_stat_from_page Message-Id: <20090109134736.a995fc49.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090109043257.GB9737@balbir.in.ibm.com> References: <20090108190818.b663ce20.nishimura@mxp.nes.nec.co.jp> <20090108191430.af89e037.nishimura@mxp.nes.nec.co.jp> <20090109043257.GB9737@balbir.in.ibm.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1134 Lines: 47 On Fri, 9 Jan 2009 10:02:57 +0530 Balbir Singh wrote: > > pc = lookup_page_cgroup(page); > > + smp_rmb(); > > Do you really need the read memory barrier? > Necessary. > > + if (!PageCgroupUsed(pc)) > > + return NULL; > > + > > In this case we've hit a case where the page is valid and the pc is > not. This does fix the problem, but won't this impact us getting > correct reclaim stats and thus indirectly impact the working of > pressure? > - If retruns NULL, only global LRU's status is updated. Because this page is not belongs to any memcg, we cannot update any counters. But yes, your point is a concern. Maybe moving acitvate_page() to == do_swap_page() { - activate_page() mem_cgroup_try_charge().. .... mem_cgroup_commit_charge().... .... + activate_page() } == is necessary. How do you think, kosaki ? Thanks, -Kame -- 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/