From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id CE9096B0005 for ; Fri, 29 Apr 2016 05:28:37 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id w143so14571435wmw.3 for ; Fri, 29 Apr 2016 02:28:37 -0700 (PDT) Received: from mail-wm0-f49.google.com (mail-wm0-f49.google.com. [74.125.82.49]) by mx.google.com with ESMTPS id m6si16351431wjz.36.2016.04.29.02.28.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Apr 2016 02:28:36 -0700 (PDT) Received: by mail-wm0-f49.google.com with SMTP id a17so26306267wme.0 for ; Fri, 29 Apr 2016 02:28:36 -0700 (PDT) Date: Fri, 29 Apr 2016 11:28:35 +0200 From: Michal Hocko 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org