From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 87CE36B0044 for ; Tue, 24 Nov 2009 09:01:22 -0500 (EST) Date: Tue, 24 Nov 2009 23:00:29 +0900 From: Daisuke Nishimura Subject: Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task in case of use_hierarchy Message-Id: <20091124230029.7245e1b8.d-nishimura@mtf.biglobe.ne.jp> In-Reply-To: <661de9470911240531p5e587c42w96995fde37dbd401@mail.gmail.com> References: <20091124145759.194cfc9f.nishimura@mxp.nes.nec.co.jp> <661de9470911240531p5e587c42w96995fde37dbd401@mail.gmail.com> Reply-To: nishimura@mxp.nes.nec.co.jp Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Balbir Singh Cc: Andrew Morton , LKML , linux-mm , stable , David Rientjes , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Daisuke Nishimura List-ID: 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: > > > > A A A A /00 A A A A A use_hierarchy == 0 A A A <- hitting limit > > A A A A A /00/aa A A use_hierarchy == 1 A A A <- "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. 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. Regards, Daisuke Nishimura. -- 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