Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751630AbdF3Ijb (ORCPT ); Fri, 30 Jun 2017 04:39:31 -0400 Received: from mx2.suse.de ([195.135.220.15]:60303 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751421AbdF3Ija (ORCPT ); Fri, 30 Jun 2017 04:39:30 -0400 Date: Fri, 30 Jun 2017 10:39:26 +0200 From: Michal Hocko To: Wei Yang Cc: Linux-MM , Andrew Morton , Mel Gorman , Vlastimil Babka , Andrea Arcangeli , Reza Arbab , Yasuaki Ishimatsu , Xishi Qiu , Kani Toshimitsu , slaoub@gmail.com, Joonsoo Kim , Daniel Kiper , Igor Mammedov , Vitaly Kuznetsov , LKML Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions Message-ID: <20170630083926.GA22923@dhcp22.suse.cz> References: <20170629073509.623-1-mhocko@kernel.org> <20170629073509.623-3-mhocko@kernel.org> 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: 3663 Lines: 97 On Fri 30-06-17 11:09:51, Wei Yang wrote: > On Thu, Jun 29, 2017 at 3:35 PM, Michal Hocko wrote: > > From: Michal Hocko > > > > Michal, > > I love the idea very much. > > > Historically we have enforced that any kernel zone (e.g ZONE_NORMAL) has > > to precede the Movable zone in the physical memory range. The purpose of > > the movable zone is, however, not bound to any physical memory restriction. > > It merely defines a class of migrateable and reclaimable memory. > > > > There are users (e.g. CMA) who might want to reserve specific physical > > memory ranges for their own purpose. Moreover our pfn walkers have to be > > prepared for zones overlapping in the physical range already because we > > do support interleaving NUMA nodes and therefore zones can interleave as > > well. This means we can allow each memory block to be associated with a > > different zone. > > > > Loosen the current onlining semantic and allow explicit onlining type on > > any memblock. That means that online_{kernel,movable} will be allowed > > regardless of the physical address of the memblock as long as it is > > offline of course. This might result in moveble zone overlapping with > > other kernel zones. Default onlining then becomes a bit tricky but still > > As here mentioned, we just remove the restriction for zone_movable. > For other zones, we still keep the restriction and the order as before. All other zones except for ZONE_NORMAL are subject of the physical memory restrictions. > Maybe the title is a little misleading. Audience may thinks no restriction > for all zones. I thought the context was clear from the fact that this is a hotplug related patch. As such we do not allow online_{dma,dma32,normal} we only allow to online into a kernel zone. I can update the wording but do not have a good idea how. [...] > As I spotted on the previous patch, after several round of online/offline, > The output of valid_zones will differ. > > For example in this case, after I offline memory37 and 41, I expect this: > > memory34/valid_zones:Normal > memory35/valid_zones:Normal Movable > memory36/valid_zones:Normal Movable > memory37/valid_zones:Normal Movable > memory38/valid_zones:Normal Movable > memory39/valid_zones:Normal Movable > memory40/valid_zones:Normal Movable > memory41/valid_zones:Normal Movable > > While the current result would be > > memory34/valid_zones:Normal > memory35/valid_zones:Normal Movable > memory36/valid_zones:Normal Movable > memory37/valid_zones:Movable Normal > memory38/valid_zones:Movable Normal > memory39/valid_zones:Movable Normal > memory40/valid_zones:Movable Normal > memory41/valid_zones:Movable Normal You haven't written your sequence of onlining but if you used the same one as mentioned in the patch then you should get memory34/valid_zones:Normal memory35/valid_zones:Normal Movable memory36/valid_zones:Normal Movable memory37/valid_zones:Normal Movable memory38/valid_zones:Normal Movable memory39/valid_zones:Normal memory40/valid_zones:Movable Normal memory41/valid_zones:Movable Normal Even if you kept 37 as movable and offline 38 you wouldn't get 38-41 movable by default because... > The reason is the same, we don't adjust the zone's range when offline > memory. .. of this. > This is also a known issue? yes and to be honest I do not plan to fix it unless somebody has a real life usecase for it. Now that we allow explicit onlininig type anywhere it seems like a reasonable behavior and this will allow us to remove quite some code which is always a good deal wrt longterm maintenance. Thanks! -- Michal Hocko SUSE Labs