From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF73BECDFB1 for ; Tue, 17 Jul 2018 14:28:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9CBF52064D for ; Tue, 17 Jul 2018 14:28:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9CBF52064D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731856AbeGQPB0 (ORCPT ); Tue, 17 Jul 2018 11:01:26 -0400 Received: from mx2.suse.de ([195.135.220.15]:47980 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729389AbeGQPB0 (ORCPT ); Tue, 17 Jul 2018 11:01:26 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 25A05AFC9; Tue, 17 Jul 2018 14:28:29 +0000 (UTC) Date: Tue, 17 Jul 2018 16:28:28 +0200 From: Michal Hocko 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 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> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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