From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752697AbcD2J2p (ORCPT ); Fri, 29 Apr 2016 05:28:45 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:37870 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355AbcD2J2n (ORCPT ); Fri, 29 Apr 2016 05:28:43 -0400 Date: Fri, 29 Apr 2016 11:28:35 +0200 From: Michal Hocko To: Andrew Morton , Vlastimil Babka Cc: Linus Torvalds , Johannes Weiner , Mel Gorman , David Rientjes , Tetsuo Handa , Joonsoo Kim , Hillf Danton , linux-mm@kvack.org, LKML , Andrea Arcangeli Subject: Re: [PATCH 09/14] mm: use compaction feedback for thp backoff conditions Message-ID: <20160429092835.GD21977@dhcp22.suse.cz> References: <1461181647-8039-1-git-send-email-mhocko@kernel.org> <1461181647-8039-10-git-send-email-mhocko@kernel.org> <5721CF7E.9020106@suse.cz> <20160428123545.GG31489@dhcp22.suse.cz> <5723267C.1050903@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5723267C.1050903@suse.cz> 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 29-04-16 11:16:44, Vlastimil Babka wrote: > On 04/28/2016 02:35 PM, Michal Hocko wrote: [...] > >My main point was to simplify the code and get rid of as much compaction > >specific hacks as possible. We might very well drop this later on but it > >would be at least less code to grasp through. I do not have any problem > >with dropping this but I think this shouldn't collide with other patches > >much so reducing the number of lines is worth it. Good point, I have completely missed this part. > I just realized it also affects khugepaged, and not just THP page faults, so > it may potentially cripple THP's completely. My main issue is that the > reasons to bail out includes COMPACT_SKIPPED, and for a wrong reason (see > the comment above). It also goes against the comment below the noretry > label: > > * High-order allocations do not necessarily loop after direct reclaim > * and reclaim/compaction depends on compaction being called after > * reclaim so call directly if necessary. > > Given that THP's are large, I expect reclaim would indeed be quite often > necessary before compaction, and the first optimistic async compaction > attempt will just return SKIPPED. After this patch, there will be no more > reclaim/compaction attempts for THP's, including khugepaged. And given the > change of THP page fault defaults, even crippling that path should no longer > be necessary. > > So I would just drop this for now indeed. Agreed, thanks for catching this. Andrew, could you drop this patch please? It was supposed to be a mere clean up without any effect on the oom detection. Thanks! -- Michal Hocko SUSE Labs