From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id F1AB06B0089 for ; Mon, 15 Feb 2010 19:26:42 -0500 (EST) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o1G0Qesj020803 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Tue, 16 Feb 2010 09:26:40 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 6406745DE61 for ; Tue, 16 Feb 2010 09:26:40 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 43C2445DE5D for ; Tue, 16 Feb 2010 09:26:40 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 1BA0D1DB8042 for ; Tue, 16 Feb 2010 09:26:40 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id C045C1DB8040 for ; Tue, 16 Feb 2010 09:26:39 +0900 (JST) Date: Tue, 16 Feb 2010 09:23:11 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [patch -mm 4/9 v2] oom: remove compulsory panic_on_oom mode Message-Id: <20100216092311.86bceb0c.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20100216090005.f362f869.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: David Rientjes Cc: Andrew Morton , Rik van Riel , Nick Piggin , Andrea Arcangeli , Balbir Singh , Lubos Lunak , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Mon, 15 Feb 2010 16:14:22 -0800 (PST) David Rientjes wrote: > On Tue, 16 Feb 2010, KAMEZAWA Hiroyuki wrote: > > > > If /proc/sys/vm/panic_on_oom is set to 2, the kernel will panic > > > regardless of whether the memory allocation is constrained by either a > > > mempolicy or cpuset. > > > > > > Since mempolicy-constrained out of memory conditions now iterate through > > > the tasklist and select a task to kill, it is possible to panic the > > > machine if all tasks sharing the same mempolicy nodes (including those > > > with default policy, they may allocate anywhere) or cpuset mems have > > > /proc/pid/oom_adj values of OOM_DISABLE. This is functionally equivalent > > > to the compulsory panic_on_oom setting of 2, so the mode is removed. > > > > > > Signed-off-by: David Rientjes > > > > NACK. In an enviroment which depends on cluster-fail-over, this is useful > > even if in such situation. > > > > You don't understand that the behavior has changed ever since > mempolicy-constrained oom conditions are now affected by a compulsory > panic_on_oom mode, please see the patch description. It's absolutely > insane for a single sysctl mode to panic the machine anytime a cpuset or > mempolicy runs out of memory and is more prone to user error from setting > it without fully understanding the ramifications than any use it will ever > do. The kernel already provides a mechanism for doing this, OOM_DISABLE. > if you want your cpuset or mempolicy to risk panicking the machine, set > all tasks that share its mems or nodes, respectively, to OOM_DISABLE. > This is no different from the memory controller being immune to such > panic_on_oom conditions, stop believing that it is the only mechanism used > in the kernel to do memory isolation. > You don't explain why "we _have to_ remove API which is used" Thanks, -Kame -- 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