From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760179AbZEGVha (ORCPT ); Thu, 7 May 2009 17:37:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752007AbZEGVhT (ORCPT ); Thu, 7 May 2009 17:37:19 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:38861 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751837AbZEGVhR (ORCPT ); Thu, 7 May 2009 17:37:17 -0400 From: "Rafael J. Wysocki" To: David Rientjes Subject: Re: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag Date: Thu, 7 May 2009 23:36:10 +0200 User-Agent: KMail/1.11.2 (Linux/2.6.30-rc4-rjw; KDE/4.2.2; x86_64; ; ) Cc: Andrew Morton , fengguang.wu@intel.com, linux-pm@lists.linux-foundation.org, pavel@ucw.cz, torvalds@linux-foundation.org, jens.axboe@oracle.com, alan-jenkins@tuffmail.co.uk, linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org References: <20090507135615.e7db550d.akpm@linux-foundation.org> In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200905072336.11383.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 07 May 2009, David Rientjes wrote: > On Thu, 7 May 2009, Andrew Morton wrote: > > > > > All of your tasks are in D state other than kthreads, right? That means > > > > they won't be in the oom killer (thus no zones are oom locked), so you can > > > > easily do this > > > > > > > > struct zone *z; > > > > for_each_populated_zone(z) > > > > zone_set_flag(z, ZONE_OOM_LOCKED); > > > > > > > > and then > > > > > > > > for_each_populated_zone(z) > > > > zone_clear_flag(z, ZONE_OOM_LOCKED); > > > > > > > > The serialization is done with trylocks so this will never invoke the oom > > > > killer because all zones in the allocator's zonelist will be oom locked. > > > > > > > > Why does this not work for you? > > > > > > Well, it might work too, but why are you insisting? How's it better than > > > __GFP_NO_OOM_KILL, actually? > > > > > > Andrew, what do you think about this? > > > > I don't think I understand the proposal. Is it to provide a means by > > which PM can go in and set a state bit against each and every zone? If > > so, that's still a global boolean, only messier. > > > > Why can't it be global while preallocating memory for hibernation since > nothing but kthreads could allocate at this point and if the system is oom > then the oom killer wouldn't be able to do anything anyway since it can't > kill them? > > The fact is that _all_ allocations here are implicitly __GFP_NO_OOM_KILL > whether it specifies it or not since the oom killer would simply kill a > task in D state which can't exit or free memory and subsequent allocations > would make the oom killer a no-op because there's an eligible task with > TIF_MEMDIE set. The only thing you're saving with __GFP_NO_OOM_KILL is > calling the oom killer in a first place and killing an unresponsive task That's exactly what we're trying to do. We don't want tasks to get killed just because we're freeing memory for hibernation image. > but that would have to happen anyway when thawed since the system is oom > (or otherwise lockup for GFP_KERNEL with order < PAGE_ALLOC_COSTLY_ORDER). Are you sure? The image memory is freed before thawing tasks.