From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) by kanga.kvack.org (Postfix) with ESMTP id CF42C6B0273 for ; Tue, 17 Jul 2018 10:28:30 -0400 (EDT) Received: by mail-ed1-f71.google.com with SMTP id y17-v6so649995eds.22 for ; Tue, 17 Jul 2018 07:28:30 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id t27-v6si1106598edd.157.2018.07.17.07.28.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Jul 2018 07:28:29 -0700 (PDT) Date: Tue, 17 Jul 2018 16:28:28 +0200 From: Michal Hocko Subject: Re: [PATCH] mm/page_alloc: Deprecate kernelcore=nn and movable_core= Message-ID: <20180717142828.GK7193@dhcp22.suse.cz> References: <20180717131837.18411-1-bhe@redhat.com> <20180717133109.GI7193@dhcp22.suse.cz> <20180717142443.GG1724@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717142443.GG1724@MiWiFi-R3L-srv> Sender: owner-linux-mm@kvack.org List-ID: To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, corbet@lwn.net, linux-doc@vger.kernel.org On Tue 17-07-18 22:24:43, Baoquan He wrote: > Hi Michal, > > On 07/17/18 at 03:31pm, Michal Hocko wrote: > > On Tue 17-07-18 21:18:37, Baoquan He wrote: > > > We can still use 'kernelcore=mirror' or 'movable_node' for the usage > > > of hotplug and movable zone. If somebody shows up with a valid usecase > > > we can reconsider. > > > > Well this doesn't really explain why to deprecate this functionality. > > It is a rather ugly hack that has been originally introduced for large > > order allocations. But we do have compaction these days. Even though the > > compaction cannot solve all the fragmentation issues the zone movable is > > not a great answer as it introduces other issues (basically highmem kind > > of issues we used to have on 32b systems). > > The current code doesn't work with KASLR and the code is too subtle to > > work properly in other cases as well. E.g. movablecore range might cover > > already used memory (e.g. bootmem allocations) and therefore it doesn't > > comply with the basic assumption that the memory is movable and that > > confuses memory hotplug (e.g. 15c30bc09085 ("mm, memory_hotplug: make > > has_unmovable_pages more robust"). > > > > There are probably other issues I am not aware of but primarily the code > > adds a maintenance burden which would be better to get rid of. > > > > I would also go further and remove all the code the feature is using at > > one go. If somebody really needs this functionality we would need to > > revert the whole thing anyway. > > Thanks for these details. I can arrange your above saying and rewrite > patch log. Are you suggesting removing the code "kernelcore=nn" and > "movablecore=" are using? If yes, I can repost with these changes. Yes. -- Michal Hocko SUSE Labs