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 SMTP id C6B526B0219 for ; Tue, 1 Jun 2010 03:37:27 -0400 (EDT) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o517bNtH011734 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Tue, 1 Jun 2010 16:37:23 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id F413645DE54 for ; Tue, 1 Jun 2010 16:37:22 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id C28AA45DE4C for ; Tue, 1 Jun 2010 16:37:22 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id A178A1DB8016 for ; Tue, 1 Jun 2010 16:37:22 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 5031A1DB801A for ; Tue, 1 Jun 2010 16:37:22 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [patch -mm 09/18] oom: add forkbomb penalty to badness heuristic In-Reply-To: References: Message-Id: <20100601163705.2460.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 1 Jun 2010 16:37:21 +0900 (JST) Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton , Rik van Riel , Nick Piggin , Oleg Nesterov , KAMEZAWA Hiroyuki , Balbir Singh , linux-mm@kvack.org List-ID: > Add a forkbomb penalty for processes that fork an excessively large > number of children to penalize that group of tasks and not others. A > threshold is configurable from userspace to determine how many first- > generation execve children (those with their own address spaces) a task > may have before it is considered a forkbomb. This can be tuned by > altering the value in /proc/sys/vm/oom_forkbomb_thres, which defaults to > 1000. > > When a task has more than 1000 first-generation children with different > address spaces than itself, a penalty of > > (average rss of children) * (# of 1st generation execve children) > ----------------------------------------------------------------- > oom_forkbomb_thres > > is assessed. So, for example, using the default oom_forkbomb_thres of > 1000, the penalty is twice the average rss of all its execve children if > there are 2000 such tasks. A task is considered to count toward the > threshold if its total runtime is less than one second; for 1000 of such > tasks to exist, the parent process must be forking at an extremely high > rate either erroneously or maliciously. > > Even though a particular task may be designated a forkbomb and selected as > the victim, the oom killer will still kill the 1st generation execve child > with the highest badness() score in its place. The avoids killing > important servers or system daemons. When a web server forks a very large > number of threads for client connections, for example, it is much better > to kill one of those threads than to kill the server and make it > unresponsive. > > [oleg@redhat.com: optimize task_lock when iterating children] > Signed-off-by: David Rientjes nack -- 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