From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 51F336B0078 for ; Wed, 17 Feb 2010 04:23:43 -0500 (EST) Received: from wpaz17.hot.corp.google.com (wpaz17.hot.corp.google.com [172.24.198.81]) by smtp-out.google.com with ESMTP id o1H9NdrX023412 for ; Wed, 17 Feb 2010 09:23:39 GMT Received: from pzk15 (pzk15.prod.google.com [10.243.19.143]) by wpaz17.hot.corp.google.com with ESMTP id o1H9NVta020712 for ; Wed, 17 Feb 2010 01:23:37 -0800 Received: by pzk15 with SMTP id 15so7000048pzk.11 for ; Wed, 17 Feb 2010 01:23:37 -0800 (PST) Date: Wed, 17 Feb 2010 01:23:35 -0800 (PST) From: David Rientjes Subject: Re: [patch 4/7 -mm] oom: badness heuristic rewrite In-Reply-To: <28c262361002162341m1d77509dv37d7d13b4ccd0ef9@mail.gmail.com> Message-ID: References: <4B73833D.5070008@redhat.com> <1265982984.6207.29.camel@barrios-desktop> <28c262361002121845w459d0fa0l55a58552c3a6081e@mail.gmail.com> <1266326086.1709.50.camel@barrios-desktop> <28c262361002162341m1d77509dv37d7d13b4ccd0ef9@mail.gmail.com> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="531381004-354184966-1266398616=:30931" Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: Rik van Riel , Andrew Morton , KAMEZAWA Hiroyuki , Nick Piggin , Andrea Arcangeli , Balbir Singh , Lubos Lunak , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --531381004-354184966-1266398616=:30931 Content-Type: TEXT/PLAIN; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Wed, 17 Feb 2010, Minchan Kim wrote: > >> Okay. I can think it of slight penalization in this patch. > >> But in current OOM logic, we try to kill child instead of forkbomb > >> itself. My concern was that. > > > > We still do with my rewrite, that is handled in oom_kill_process(). A The > > forkbomb penalization takes place in badness(). > > > I thought this patch is closely related to [patch 2/7]. > I can move this discussion to [patch 2/7] if you want. > Another guys already pointed out why we care child. > We have _always_ tried to kill a child of the selected task first if it has a seperate address space, patch 2 doesn't change that. It simply tries to kill the child with the highest badness() score. > I said this scenario is BUGGY forkbomb process. It will fork + exec continuously > if it isn't killed. How does user intervene to fix the system? > System was almost hang due to unresponsive. > The user would need to kill the parent if it should be killed. The unresponsiveness in this example, however, is not a question of the oom killer but rather the scheduler to provide interactivity to the user in forkbomb scenarios. The oom killer should not create a policy that unfairly biases tasks that fork a large number of tasks, however, to provide interactivity since that task may be a vital system resource. > For extreme example, > User is writing some important document by OpenOffice and > he decided to execute hackbench 1000000 process 1000000. > > Could user save his important office data without halt if we kill > child continuously? > I think this scenario can be happened enough if the user didn't know > parameter of hackbench. > So what exactly are you proposing we do in the oom killer to distinguish between a user's mistake and a vital system resource? I'm personally much more concerned with protecting system daemons that provide a service under heavyload than protecting against forkbombs in the oom killer. --531381004-354184966-1266398616=:30931-- -- 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