Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932080AbdGNMSH (ORCPT ); Fri, 14 Jul 2017 08:18:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:46199 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753624AbdGNMSF (ORCPT ); Fri, 14 Jul 2017 08:18:05 -0400 Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions To: Michal Hocko , Andrew Morton Cc: 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 , linux-mm@kvack.org, LKML , Michal Hocko , Joonsoo Kim , linux-api@vger.kernel.org References: <20170714121233.16861-1-mhocko@kernel.org> <20170714121233.16861-3-mhocko@kernel.org> From: Vlastimil Babka Message-ID: Date: Fri, 14 Jul 2017 14:17:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170714121233.16861-3-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4644 Lines: 109 On 07/14/2017 02:12 PM, Michal Hocko wrote: > From: Michal Hocko > > 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 > sensible. echo online > memoryXY/state will online the given block to > 1) the default zone if the given range is outside of any zone > 2) the enclosing zone if such a zone doesn't interleave with > any other zone > 3) the default zone if more zones interleave for this range > where default zone is movable zone only if movable_node is enabled > otherwise it is a kernel zone. > > Here is an example of the semantic with (movable_node is not present but > it work in an analogous way). We start with following memblocks, all of > them offline > memory34/valid_zones:Normal Movable > 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 > > Now, we online block 34 in default mode and block 37 as movable > root@test1:/sys/devices/system/node/node1# echo online > memory34/state > root@test1:/sys/devices/system/node/node1# echo online_movable > memory37/state > memory34/valid_zones:Normal > memory35/valid_zones:Normal Movable > memory36/valid_zones:Normal Movable > memory37/valid_zones:Movable > memory38/valid_zones:Normal Movable > memory39/valid_zones:Normal Movable > memory40/valid_zones:Normal Movable > memory41/valid_zones:Normal Movable > > As we can see all other blocks can still be onlined both into Normal and > Movable zones and the Normal is default because the Movable zone spans > only block37 now. > root@test1:/sys/devices/system/node/node1# echo online_movable > memory41/state > memory34/valid_zones:Normal > memory35/valid_zones:Normal Movable > memory36/valid_zones:Normal Movable > memory37/valid_zones:Movable > memory38/valid_zones:Movable Normal > memory39/valid_zones:Movable Normal > memory40/valid_zones:Movable Normal > memory41/valid_zones:Movable > > Now the default zone for blocks 37-41 has changed because movable zone > spans that range. > root@test1:/sys/devices/system/node/node1# echo online_kernel > memory39/state > memory34/valid_zones:Normal > memory35/valid_zones:Normal Movable > memory36/valid_zones:Normal Movable > memory37/valid_zones:Movable > memory38/valid_zones:Normal Movable > memory39/valid_zones:Normal > memory40/valid_zones:Movable Normal > memory41/valid_zones:Movable > > Note that the block 39 now belongs to the zone Normal and so block38 > falls into Normal by default as well. > > For completness > root@test1:/sys/devices/system/node/node1# for i in memory[34]? > do > echo online > $i/state 2>/dev/null > done > > memory34/valid_zones:Normal > memory35/valid_zones:Normal > memory36/valid_zones:Normal > memory37/valid_zones:Movable > memory38/valid_zones:Normal > memory39/valid_zones:Normal > memory40/valid_zones:Movable > memory41/valid_zones:Movable > > Implementation wise the change is quite straightforward. We can get rid > of allow_online_pfn_range altogether. online_pages allows only offline > nodes already. The original default_zone_for_pfn will become > default_kernel_zone_for_pfn. New default_zone_for_pfn implements the > above semantic. zone_for_pfn_range is slightly reorganized to implement > kernel and movable online type explicitly and MMOP_ONLINE_KEEP becomes > a catch all default behavior. > > Acked-by: Joonsoo Kim Acked-by: Vlastimil Babka > Cc: > Signed-off-by: Michal Hocko