From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934603AbdERRYh (ORCPT ); Thu, 18 May 2017 13:24:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:42951 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932421AbdERRYe (ORCPT ); Thu, 18 May 2017 13:24:34 -0400 Date: Thu, 18 May 2017 19:24:24 +0200 From: Michal Hocko To: Christoph Lameter Cc: Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Li Zefan , Mel Gorman , David Rientjes , Hugh Dickins , Andrea Arcangeli , Anshuman Khandual , "Kirill A. Shutemov" , linux-api@vger.kernel.org Subject: Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with cpuset update Message-ID: <20170518172424.GB30148@dhcp22.suse.cz> References: <20170517092042.GH18247@dhcp22.suse.cz> <20170517140501.GM18247@dhcp22.suse.cz> <20170517145645.GO18247@dhcp22.suse.cz> <20170518090846.GD25462@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 18-05-17 11:57:55, Cristopher Lameter wrote: > On Thu, 18 May 2017, Michal Hocko wrote: > > > > Nope. The OOM in a cpuset gets the process doing the alloc killed. Or what > > > that changed? > > !!!!! > > > > > > > At this point you have messed up royally and nothing is going to rescue > > > you anyways. OOM or not does not matter anymore. The app will fail. > > > > Not really. If you can trick the system to _think_ that the intersection > > between mempolicy and the cpuset is empty then the OOM killer might > > trigger an innocent task rather than the one which tricked it into that > > situation. > > See above. OOM Kill in a cpuset does not kill an innocent task but a task > that does an allocation in that specific context meaning a task in that > cpuset that also has a memory policty. No, the oom killer will chose the largest task in the specific NUMA domain. If you just fail such an allocation then a page fault would get VM_FAULT_OOM and pagefault_out_of_memory would kill a task regardless of the cpusets. > Regardless of that the point earlier was that the moving logic can avoid > creating temporary situations of empty sets of nodes by analysing the > memory policies etc and only performing moves when doing so is safe. How are you going to do that in a raceless way? Moreover the whole discussion is about _failing_ allocations on an empty cpuset and mempolicy intersection. -- Michal Hocko SUSE Labs