From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753091AbZEKNix (ORCPT ); Mon, 11 May 2009 09:38:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750943AbZEKNio (ORCPT ); Mon, 11 May 2009 09:38:44 -0400 Received: from gir.skynet.ie ([193.1.99.77]:45028 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751404AbZEKNin (ORCPT ); Mon, 11 May 2009 09:38:43 -0400 Date: Mon, 11 May 2009 14:38:40 +0100 From: Mel Gorman To: Minchan Kim Cc: David Rientjes , Andrew Morton , Peter Zijlstra , Nick Piggin , Christoph Lameter , Dave Hansen , linux-kernel@vger.kernel.org Subject: Re: [patch -mmotm] mm: invoke oom killer for __GFP_NOFAIL Message-ID: <20090511133840.GA11624@csn.ul.ie> References: <20090511162900.f372edd1.minchan.kim@barrios-desktop> <28c262360905110212j9867b79wd8d90b16f6f196be@mail.gmail.com> <28c262360905110421g1b079f2cr798ca95adfb8ee45@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <28c262360905110421g1b079f2cr798ca95adfb8ee45@mail.gmail.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 11, 2009 at 08:21:21PM +0900, Minchan Kim wrote: > On Mon, May 11, 2009 at 6:12 PM, Minchan Kim wrote: > > On Mon, May 11, 2009 at 5:40 PM, David Rientjes wrote: > >> On Mon, 11 May 2009, Minchan Kim wrote: > >> > >>> Hmm.. if __alloc_pages_may_oom fail to allocate free page due to order > PAGE_ALLOC_COSTRY_ORDER, > >>> > >>> It will go to nopage label in __alloc_pages_slowpath. > >>> Then it will show the page allocation failure warning and will return. > >>> Retrying depends on caller. > >>> > >> > >> Correct. > >> > >>> So, I think it won't loop forever. > >>> Do I miss something ? > >>> > >> > >> __GFP_NOFAIL allocations shouldn't fail, that's the point of the gfp flag. > >> So failing without attempting to free some memory is the wrong thing to > >> do. > > > > Thanks for quick reply. > > I was confused by your description. > > I thought you suggested we have to prevent loop forever. > > > >> > >>> In addition, the OOM killer can help for getting the high order pages ? > >>> > >> > >> Sure, if it selects a task that will free a lot of memory, which is it's > >> goal. > >> > > > > How do we know any task have a lot of memory ? > > If we select wrong task and kill one ? > > > > I have a concern about innocent task. > > Now, I look over __out_of_memory. > For selecting better tasks in case of PAGE_ALLOC_COSTRY_ORDER, How > about increasing score of task which have VM_HUGETLB vma in badness ? > That is unjustified. It penalises a process even if it only allocated one hugepage and it is not a reflection of how much memory the process is using or how badly behaved it is. Even worse, if the huge page was allocated from the static hugepage pool then the hugepages are freed to the hugepage pool and not the page allocator when the process is killed. This means that killing a process using hugepages does not necessarily help applications requiring more memory unless they also want hugepages. However, a hugepage allocation will not trigger the OOM killer so killing processes using hugepages still does not help. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab