Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753615AbcL3LFv (ORCPT ); Fri, 30 Dec 2016 06:05:51 -0500 Received: from mx2.suse.de ([195.135.220.15]:47663 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750830AbcL3LFu (ORCPT ); Fri, 30 Dec 2016 06:05:50 -0500 Date: Fri, 30 Dec 2016 12:05:45 +0100 From: Michal Hocko To: Mel Gorman Cc: Nils Holland , Johannes Weiner , Vladimir Davydov , Tetsuo Handa , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Chris Mason , David Sterba , linux-btrfs@vger.kernel.org Subject: Re: [RFC PATCH] mm, memcg: fix (Re: OOM: Better, but still there on) Message-ID: <20161230110545.GF13301@dhcp22.suse.cz> References: <20161222101028.GA11105@ppc-nas.fritz.box> <20161222191719.GA19898@dhcp22.suse.cz> <20161222214611.GA3015@boerne.fritz.box> <20161223105157.GB23109@dhcp22.suse.cz> <20161223121851.GA27413@ppc-nas.fritz.box> <20161223125728.GE23109@dhcp22.suse.cz> <20161223144738.GB23117@dhcp22.suse.cz> <20161223222559.GA5568@teela.multi.box> <20161226124839.GB20715@dhcp22.suse.cz> <20161230101926.jjjw76negqcvyaim@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161230101926.jjjw76negqcvyaim@suse.de> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3729 Lines: 90 On Fri 30-12-16 10:19:26, Mel Gorman wrote: > On Mon, Dec 26, 2016 at 01:48:40PM +0100, Michal Hocko wrote: > > On Fri 23-12-16 23:26:00, Nils Holland wrote: > > > On Fri, Dec 23, 2016 at 03:47:39PM +0100, Michal Hocko wrote: > > > > > > > > Nils, even though this is still highly experimental, could you give it a > > > > try please? > > > > > > Yes, no problem! So I kept the very first patch you sent but had to > > > revert the latest version of the debugging patch (the one in > > > which you added the "mm_vmscan_inactive_list_is_low" event) because > > > otherwise the patch you just sent wouldn't apply. Then I rebooted with > > > memory cgroups enabled again, and the first thing that strikes the eye > > > is that I get this during boot: > > > > > > [ 1.568174] ------------[ cut here ]------------ > > > [ 1.568327] WARNING: CPU: 0 PID: 1 at mm/memcontrol.c:1032 mem_cgroup_update_lru_size+0x118/0x130 > > > [ 1.568543] mem_cgroup_update_lru_size(f4406400, 2, 1): lru_size 0 but not empty > > > > Ohh, I can see what is wrong! a) there is a bug in the accounting in > > my patch (I double account) and b) the detection for the empty list > > cannot work after my change because per node zone will not match per > > zone statistics. The updated patch is below. So I hope my brain already > > works after it's been mostly off last few days... > > --- > > From 397adf46917b2d9493180354a7b0182aee280a8b Mon Sep 17 00:00:00 2001 > > From: Michal Hocko > > Date: Fri, 23 Dec 2016 15:11:54 +0100 > > Subject: [PATCH] mm, memcg: fix the active list aging for lowmem requests when > > memcg is enabled > > > > Nils Holland has reported unexpected OOM killer invocations with 32b > > kernel starting with 4.8 kernels > > > > I think it's unfortunate that per-zone stats are reintroduced to the > memcg structure. the original patch I had didn't add per zone stats but rather did a nr_highmem counter to mem_cgroup_per_node (inside ifdeff CONFIG_HIGMEM). This would help for this particular case but it wouldn't work for other lowmem requests (e.g. GFP_DMA32) and with the kmem accounting this might be a problem in future. So I've decided to go with a more generic approach which requires per-zone tracking. I cannot say I would be overly happy about this at all. > I can't help but think that it would have also worked > to always rotate a small number of pages if !inactive_list_is_low and > reclaiming for memcg even if it distorted page aging. I am not really sure how that would work. Do you mean something like the following? diff --git a/mm/vmscan.c b/mm/vmscan.c index fa30010a5277..563ada3c02ac 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2044,6 +2044,9 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file, inactive = lruvec_lru_size(lruvec, file * LRU_FILE); active = lruvec_lru_size(lruvec, file * LRU_FILE + LRU_ACTIVE); + if (!mem_cgroup_disabled()) + goto out; + /* * For zone-constrained allocations, it is necessary to check if * deactivations are required for lowmem to be reclaimed. This @@ -2063,6 +2066,7 @@ static bool inactive_list_is_low(struct lruvec *lruvec, bool file, active -= min(active, active_zone); } +out: gb = (inactive + active) >> (30 - PAGE_SHIFT); if (gb) inactive_ratio = int_sqrt(10 * gb); The problem I see with such an approach is that chances are that this would reintroduce what f8d1a31163fc ("mm: consider whether to decivate based on eligible zones inactive ratio") tried to fix. But maybe I have missed your point. > However, given that such an approach would be less robust and this has > been heavily tested; > > Acked-by: Mel Gorman Thanks! -- Michal Hocko SUSE Labs