From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759608AbbJ3Kie (ORCPT ); Fri, 30 Oct 2015 06:38:34 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:37151 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759587AbbJ3Kic (ORCPT ); Fri, 30 Oct 2015 06:38:32 -0400 Date: Fri, 30 Oct 2015 11:38:30 +0100 From: Michal Hocko To: "Huang, Ying" Cc: Mel Gorman , lkp@01.org, LKML , Andrew Morton , Rik van Riel , Vitaly Wool , David Rientjes , Christoph Lameter , Johannes Weiner , Vlastimil Babka , Stephen Rothwell Subject: Re: [lkp] [mm, page_alloc] 43993977ba: +88% OOM possibility Message-ID: <20151030103830.GJ18429@dhcp22.suse.cz> References: <87oafjpnb1.fsf@yhuang-dev.intel.com> <20151029142440.GE23598@dhcp22.suse.cz> <87si4szrzf.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87si4szrzf.fsf@yhuang-dev.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 30-10-15 16:21:40, Huang, Ying wrote: > Michal Hocko writes: > > > On Wed 28-10-15 13:36:02, kernel test robot wrote: > >> FYI, we noticed the below changes on > >> > >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > >> commit 43993977baecd838d66ccabc7f682342fc6ff635 ("mm, page_alloc: > >> distinguish between being unable to sleep, unwilling to sleep and > >> avoiding waking kswapd") > >> > >> We found the OOM possibility increased 88% in a virtual machine with 1G memory. > > > > Could you provide dmesg output from this test? > > Sure, Attached. I can only see a single allocation failure warning: kworker/u4:1: page allocation failure: order:0, mode:0x2204000 This is obviously a non sleeping allocation with ___GFP_KSWAPD_RECLAIM set. ___GFP_HIGH (aka access to memory reserves) is not required so a failure of such an allocation is something to be expected. [ 2294.616369] Workqueue: btrfs-submit btrfs_submit_helper [ 2294.616369] 0000000000000000 ffff88000d38f5e0 ffffffff8173f84c 0000000000000000 [ 2294.616369] ffff88000d38f678 ffffffff811abaee 00000000ffffffff 000000010038f618 [ 2294.616369] ffff8800584e4148 00000000ffffffff ffff8800584e2f00 0000000000000001 [ 2294.616369] Call Trace: [ 2294.616369] [] dump_stack+0x4b/0x63 [ 2294.616369] [] warn_alloc_failed+0x125/0x13d [ 2294.616369] [] __alloc_pages_nodemask+0x7c9/0x915 [ 2294.616369] [] kmem_getpages+0x91/0x155 [ 2294.616369] [] fallback_alloc+0x1cc/0x24c [ 2294.616369] [] ____cache_alloc_node+0x151/0x160 [ 2294.616369] [] __kmalloc+0xb0/0x134 [ 2294.616369] [] ? sched_clock+0x9/0xb [ 2294.616369] [] ? virtqueue_add+0x78/0x37f [ 2294.616369] [] virtqueue_add+0x78/0x37f [ 2294.616369] [] ? __lock_acquire+0x751/0xf55 [ 2294.616369] [] virtqueue_add_sgs+0x76/0x85 The patch you are referring shouldn't make any change in this path because alloc_indirect which I expect is the allocation failing here does: gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH) and that came in via b92b1b89a33c ("virtio: force vring descriptors to be allocated from lowmem"). Are there more failed allocations during the test? The subject would suggest so. Thanks! -- Michal Hocko SUSE Labs