From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752511AbdARJq5 (ORCPT ); Wed, 18 Jan 2017 04:46:57 -0500 Received: from outbound-smtp07.blacknight.com ([46.22.139.12]:51347 "EHLO outbound-smtp07.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752206AbdARJq2 (ORCPT ); Wed, 18 Jan 2017 04:46:28 -0500 Date: Wed, 18 Jan 2017 09:46:15 +0000 From: Mel Gorman To: Vlastimil Babka Cc: Ganapatrao Kulkarni , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC 2/4] mm, page_alloc: fix fast-path race with cpuset update or removal Message-ID: <20170118094615.eif2xez65hpmvdnr@techsingularity.net> References: <20170117221610.22505-1-vbabka@suse.cz> <20170117221610.22505-3-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170117221610.22505-3-vbabka@suse.cz> User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 17, 2017 at 11:16:08PM +0100, Vlastimil Babka wrote: > Ganapatrao Kulkarni reported that the LTP test cpuset01 in stress mode triggers > OOM killer in few seconds, despite lots of free memory. The test attemps to > repeatedly fault in memory in one process in a cpuset, while changing allowed > nodes of the cpuset between 0 and 1 in another process. > > One possible cause is that in the fast path we find the preferred zoneref > according to current mems_allowed, so that it points to the middle of the > zonelist, skipping e.g. zones of node 1 completely. If the mems_allowed is > updated to contain only node 1, we never reach it in the zonelist, and trigger > OOM before checking the cpuset_mems_cookie. > > This patch fixes the particular case by redoing the preferred zoneref search > if we switch back to the original nodemask. The condition is also slightly > changed so that when the last non-root cpuset is removed, we don't miss it. > > Note that this is not a full fix, and more patches will follow. > > Reported-by: Ganapatrao Kulkarni > Fixes: 682a3385e773 ("mm, page_alloc: inline the fast path of the zonelist iterator") > Signed-off-by: Vlastimil Babka Acked-by: Mel Gorman -- Mel Gorman SUSE Labs