Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753695AbdGJMad (ORCPT ); Mon, 10 Jul 2017 08:30:33 -0400 Received: from mx2.suse.de ([195.135.220.15]:44868 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752227AbdGJMab (ORCPT ); Mon, 10 Jul 2017 08:30:31 -0400 Date: Mon, 10 Jul 2017 14:30:28 +0200 From: Michal Hocko To: Vlastimil Babka Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Andrea Arcangeli , Reza Arbab , Yasuaki Ishimatsu , qiuxishi@huawei.com, Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , Wei Yang , LKML , Linux API Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Message-ID: <20170710123028.GH19185@dhcp22.suse.cz> References: <20170629073509.623-1-mhocko@kernel.org> <20170629073509.623-3-mhocko@kernel.org> <64e889ae-24ab-b845-5751-978a76dd0dd9@suse.cz> <20170710064540.GA19185@dhcp22.suse.cz> <24c3606d-837a-266d-a294-7e100d1430f0@suse.cz> <20170710111750.GG19185@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1847 Lines: 43 On Mon 10-07-17 14:12:09, Vlastimil Babka wrote: > On 07/10/2017 01:17 PM, Michal Hocko wrote: > > On Mon 10-07-17 13:11:29, Vlastimil Babka wrote: > >> On 07/10/2017 08:45 AM, Michal Hocko wrote: > >>> On Fri 07-07-17 17:02:59, Vlastimil Babka wrote: > >>>> [+CC linux-api] > >>>> > >>>> > >>>> Hm so previously, blocks 37-41 would only allow Movable at this point, right? > >>> > >>> yes > >>> > >>>> Shouldn't we still default to Movable for them? We might be breaking some > >>>> existing userspace here. > >>> > >>> I do not think so. Prior to this merge window f1dd2cd13c4b ("mm, > >>> memory_hotplug: do not associate hotadded memory to zones until online") > >>> we allowed only the last offline or the adjacent to existing movable > >>> memory block to be onlined movable. So the above wasn't possible. > >> > >> Not exactly the above, but let's say 1-34 is onlined as Normal, 35-37 is > >> Movable. Then the only possible action before would be online 38 as > >> Movable? Now it defaults to Normal? > > > > Yes. And let me repeat you couldn't onlne 35-37 as movable before. So no > > userspace could depend on that before the rework. Or do I still miss > > your point? > > Ah, I see. "the last offline or the adjacent to existing movable". OK then. > > It would be indeed better to not change behavour twice then and merge > this to 4.13, but it's the middle of merge window, so it's not simple... yeah. I was thinking about about how to make the change reasonably incremental but failed to find a way. I also didn't want to bring too many changes at once (the code base is just too fragile already). If there is a general consensus about the semantic we might want to push the patch this week. I just do not want to rush it too much as this is a users visible change and it might kick us back in future. -- Michal Hocko SUSE Labs