Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932074AbdGJNRk (ORCPT ); Mon, 10 Jul 2017 09:17:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:48824 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753563AbdGJNRj (ORCPT ); Mon, 10 Jul 2017 09:17:39 -0400 Subject: Re: [PATCH] mm, vmscan: do not loop on too_many_isolated for ever To: Michal Hocko , Andrew Morton Cc: Mel Gorman , Tetsuo Handa , Rik van Riel , Johannes Weiner , linux-mm@kvack.org, LKML , Michal Hocko References: <20170710074842.23175-1-mhocko@kernel.org> From: Vlastimil Babka Message-ID: <841988a5-d3a8-3e1c-5b41-cb07df8dae96@suse.cz> Date: Mon, 10 Jul 2017 15:16:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170710074842.23175-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2199 Lines: 42 On 07/10/2017 09:48 AM, Michal Hocko wrote: > From: Michal Hocko > > Tetsuo Handa has reported [1][2][3]that direct reclaimers might get stuck > in too_many_isolated loop basically for ever because the last few pages > on the LRU lists are isolated by the kswapd which is stuck on fs locks > when doing the pageout or slab reclaim. This in turn means that there is > nobody to actually trigger the oom killer and the system is basically > unusable. > > too_many_isolated has been introduced by 35cd78156c49 ("vmscan: throttle > direct reclaim when too many pages are isolated already") to prevent > from pre-mature oom killer invocations because back then no reclaim > progress could indeed trigger the OOM killer too early. But since the > oom detection rework 0a0337e0d1d1 ("mm, oom: rework oom detection") > the allocation/reclaim retry loop considers all the reclaimable pages > and throttles the allocation at that layer so we can loosen the direct > reclaim throttling. > > Make shrink_inactive_list loop over too_many_isolated bounded and returns > immediately when the situation hasn't resolved after the first sleep. > Replace congestion_wait by a simple schedule_timeout_interruptible because > we are not really waiting on the IO congestion in this path. > > Please note that this patch can theoretically cause the OOM killer to > trigger earlier while there are many pages isolated for the reclaim > which makes progress only very slowly. This would be obvious from the oom > report as the number of isolated pages are printed there. If we ever hit > this should_reclaim_retry should consider those numbers in the evaluation > in one way or another. > > [1] http://lkml.kernel.org/r/201602092349.ACG81273.OSVtMJQHLOFOFF@I-love.SAKURA.ne.jp > [2] http://lkml.kernel.org/r/201702212335.DJB30777.JOFMHSFtVLQOOF@I-love.SAKURA.ne.jp > [3] http://lkml.kernel.org/r/201706300914.CEH95859.FMQOLVFHJFtOOS@I-love.SAKURA.ne.jp > > Acked-by: Mel Gorman > Tested-by: Tetsuo Handa > Signed-off-by: Michal Hocko Let's hope there won't be premature OOM's then. Acked-by: Vlastimil Babka