Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754924AbdDFQzf (ORCPT ); Thu, 6 Apr 2017 12:55:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:38619 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbdDFQz0 (ORCPT ); Thu, 6 Apr 2017 12:55:26 -0400 Date: Thu, 6 Apr 2017 17:55:20 +0100 From: Mel Gorman To: Michal Hocko Cc: Reza Arbab , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Andrea Arcangeli , Yasuaki Ishimatsu , Tang Chen , qiuxishi@huawei.com, Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Andi Kleen , Zhang Zhen , David Rientjes , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , LKML , Chris Metcalf , Dan Williams , Heiko Carstens , Lai Jiangshan , Martin Schwidefsky Subject: Re: [PATCH 0/6] mm: make movable onlining suck less Message-ID: <20170406165520.qjdqclsm6zl6m6p3@suse.de> References: <20170330115454.32154-1-mhocko@kernel.org> <20170406130846.GL5497@dhcp22.suse.cz> <20170406152449.zmghwdb4y6hxn4pm@arbab-laptop> <20170406154127.GQ5497@dhcp22.suse.cz> <20170406154653.yv4i2k2r7hjq6mke@arbab-laptop> <20170406162154.GR5497@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170406162154.GR5497@dhcp22.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 Content-Length: 2872 Lines: 67 On Thu, Apr 06, 2017 at 06:21:55PM +0200, Michal Hocko wrote: > > This was my first time using your git branch instead of applying the patches > > from this thread to v4.11-rc5 myself. > > OK, so this looks like another thing to resolve. I have seen this > warning as well but I didn't consider it relevant because I had to tweak > the code make the node go offline (removed check_and_unmap_cpu_on_node > from try_offline_node) so I thought it was a fallout from there. > > But let's have a look. hotadd_new_pgdat does for an existing pgdat > /* Reset the nr_zones, order and classzone_idx before reuse */ > pgdat->nr_zones = 0; > pgdat->kswapd_order = 0; > pgdat->kswapd_classzone_idx = MAX_NR_ZONES; > > so free_area_init_node absolutely has to hit this warning. This is not > in the Linus tree because it is still in Andrew's mmotm coming from > http://www.ozlabs.org/~akpm/mmotm/broken-out/mm-vmscan-prevent-kswapd-sleeping-prematurely-due-to-mismatched-classzone_idx.patch > > So yay, finally that doesn't come from me. Mel, I guess that either > hotadd_new_pgdat should keep its kswapd_classzone_idx = 0 or the warning > should be updated. > Actually, it's obvious very quickly when I started the fix that updating the warning would then trigger on normal boot. It's more appropriate to let a hotadd of a new pgdat defer the initialisation of that field to kswapd starting for the new node. Can you try this? It's build/boot tested only, no hotplug testing. ---8<--- mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx -fix The patch "mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx" has different initial starting conditions when kswapd is asleep. kswapd initialises it properly when it starts but the patch initialises kswapd_classzone_idx early and trips on a warning in free_area_init_node. This patch leaves the kswapd_classzone_idx as zero and defers to kswapd to initialise it properly when it starts. This is a fix to the mmotm patch mm-vmscan-prevent-kswapd-sleeping-prematurely-due-to-mismatched-classzone_idx.patch Signed-off-by: Mel Gorman diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 2309a7fbec93..76d4745513ee 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1214,10 +1214,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start) arch_refresh_nodedata(nid, pgdat); } else { - /* Reset the nr_zones, order and classzone_idx before reuse */ + /* + * Reset the nr_zones, order and classzone_idx before reuse. + * Note that kswapd will init kswapd_classzone_idx properly + * when it starts in the near future. + */ pgdat->nr_zones = 0; pgdat->kswapd_order = 0; - pgdat->kswapd_classzone_idx = MAX_NR_ZONES; + pgdat->kswapd_classzone_idx = 0; } /* we can use NODE_DATA(nid) from here */