Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754542AbdCIOc2 (ORCPT ); Thu, 9 Mar 2017 09:32:28 -0500 Received: from mx2.suse.de ([195.135.220.15]:50110 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754699AbdCIOcH (ORCPT ); Thu, 9 Mar 2017 09:32:07 -0500 Date: Thu, 9 Mar 2017 14:31:48 +0000 From: Mel Gorman To: Michal Hocko Cc: Andrew Morton , Johannes Weiner , Vlastimil Babka , Tetsuo Handa , Rik van Riel , linux-mm@kvack.org, LKML , Michal Hocko Subject: Re: [PATCH] mm, vmscan: do not loop on too_many_isolated for ever Message-ID: <20170309143148.ewpatb26g6lzsx6a@suse.de> References: <20170307133057.26182-1-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20170307133057.26182-1-mhocko@kernel.org> 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: 1996 Lines: 41 On Tue, Mar 07, 2017 at 02:30:57PM +0100, Michal Hocko wrote: > From: Michal Hocko > > Tetsuo Handa has reported [1][2] 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 > > Signed-off-by: Michal Hocko Acked-by: Mel Gorman -- Mel Gorman SUSE Labs