Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751817AbdF3DKO (ORCPT ); Thu, 29 Jun 2017 23:10:14 -0400 Received: from mail-vk0-f51.google.com ([209.85.213.51]:36574 "EHLO mail-vk0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751650AbdF3DKN (ORCPT ); Thu, 29 Jun 2017 23:10:13 -0400 MIME-Version: 1.0 In-Reply-To: <20170629073509.623-3-mhocko@kernel.org> References: <20170629073509.623-1-mhocko@kernel.org> <20170629073509.623-3-mhocko@kernel.org> From: Wei Yang Date: Fri, 30 Jun 2017 11:09:51 +0800 Message-ID: Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove zone restrictions To: Michal Hocko 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 , Michal Hocko Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5750 Lines: 148 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. Maybe the title is a little misleading. Audience may thinks no restriction for all zones. > 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 > 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 The reason is the same, we don't adjust the zone's range when offline memory. This is also a known issue? > 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. > > Signed-off-by: Michal Hocko > ---