From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 9F9D06B007B for ; Tue, 24 Nov 2009 12:04:15 -0500 (EST) Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [202.81.31.247]) by e23smtp03.au.ibm.com (8.14.3/8.13.1) with ESMTP id nAOH1QRj027678 for ; Wed, 25 Nov 2009 04:01:26 +1100 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nAOH0bhW1421448 for ; Wed, 25 Nov 2009 04:00:39 +1100 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nAOH46WU006750 for ; Wed, 25 Nov 2009 04:04:07 +1100 Date: Tue, 24 Nov 2009 22:34:02 +0530 From: Balbir Singh Subject: Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task in case of use_hierarchy Message-ID: <20091124170402.GB3365@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20091124145759.194cfc9f.nishimura@mxp.nes.nec.co.jp> <661de9470911240531p5e587c42w96995fde37dbd401@mail.gmail.com> <20091124230029.7245e1b8.d-nishimura@mtf.biglobe.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20091124230029.7245e1b8.d-nishimura@mtf.biglobe.ne.jp> Sender: owner-linux-mm@kvack.org To: nishimura@mxp.nes.nec.co.jp Cc: Andrew Morton , LKML , linux-mm , stable , David Rientjes , KAMEZAWA Hiroyuki , KOSAKI Motohiro List-ID: * Daisuke Nishimura [2009-11-24 23:00:29]: > On Tue, 24 Nov 2009 19:01:54 +0530 > Balbir Singh wrote: > > > On Tue, Nov 24, 2009 at 11:27 AM, Daisuke Nishimura > > wrote: > > > task_in_mem_cgroup(), which is called by select_bad_process() to check whether > > > a task can be a candidate for being oom-killed from memcg's limit, checks > > > "curr->use_hierarchy"("curr" is the mem_cgroup the task belongs to). > > > > > > But this check return true(it's false positive) when: > > > > > > /00 use_hierarchy == 0 <- hitting limit > > > /00/aa use_hierarchy == 1 <- "curr" > > > > > > This leads to killing an innocent task in 00/aa. This patch is a fix for this > > > bug. And this patch also fixes the arg for mem_cgroup_print_oom_info(). We > > > should print information of mem_cgroup which the task being killed, not current, > > > belongs to. > > > > > > > Quick Question: What happens if /00 has no tasks in it > > after your patches? > > > Nothing would happen because /00 never hit its limit. Why not? I am talking of a scenario where /00 is set to a limit (similar to your example) and hits its limit, but the groups under it have no limits, but tasks. Shouldn't we be scanning /00/aa as well? > > The bug that this patch fixes is: > > - create a dir /00 and set some limits. > - create a sub dir /00/aa w/o any limits, and enable hierarchy. > - run some programs in both in 00 and 00/aa. programs in 00 should be > big enough to cause oom by its limit. > - when oom happens by 00's limit, tasks in 00/aa can also be killed. > To be honest, the last part is fair, specifically if 00/aa has a task that is really the heaviest task as per the oom logic. no? Are you suggesting that only tasks in /00 should be selected by the oom logic? -- Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org