From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id 55A796B026F for ; Tue, 17 Jul 2018 10:24:53 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id o18-v6so895504qko.21 for ; Tue, 17 Jul 2018 07:24:53 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id i3-v6si1031537qvg.215.2018.07.17.07.24.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Jul 2018 07:24:52 -0700 (PDT) Date: Tue, 17 Jul 2018 22:24:43 +0800 From: Baoquan He Subject: Re: [PATCH] mm/page_alloc: Deprecate kernelcore=nn and movable_core= Message-ID: <20180717142443.GG1724@MiWiFi-R3L-srv> References: <20180717131837.18411-1-bhe@redhat.com> <20180717133109.GI7193@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180717133109.GI7193@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, corbet@lwn.net, linux-doc@vger.kernel.org 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. Just saw some deprecated codes are still there for future cleaning up. So posted this v1 patch. Thanks Baoquan > > --- > > Documentation/admin-guide/kernel-parameters.txt | 2 ++ > > mm/page_alloc.c | 3 +++ > > 2 files changed, 5 insertions(+) > > > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > > index efc7aa7a0670..1e22c49866a2 100644 > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -1855,6 +1855,7 @@ > > keepinitrd [HW,ARM] > > > > kernelcore= [KNL,X86,IA-64,PPC] > > + [Usage of kernelcore=nn[KMGTPE] | nn% is deprecated] > > Format: nn[KMGTPE] | nn% | "mirror" > > This parameter specifies the amount of memory usable by > > the kernel for non-movable allocations. The requested > > @@ -2395,6 +2396,7 @@ > > reporting absolute coordinates, such as tablets > > > > movablecore= [KNL,X86,IA-64,PPC] > > + [Deprecated] > > Format: nn[KMGTPE] | nn% > > This parameter is the complement to kernelcore=, it > > specifies the amount of memory used for migratable > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 1521100f1e63..86cf05f48b5f 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -6899,6 +6899,8 @@ static int __init cmdline_parse_kernelcore(char *p) > > return 0; > > } > > > > + pr_warn("Only kernelcore=mirror supported, " > > + "usage of kernelcore=nn[KMGTPE]|nn%% is deprecated.\n"); > > return cmdline_parse_core(p, &required_kernelcore, > > &required_kernelcore_percent); > > } > > @@ -6909,6 +6911,7 @@ static int __init cmdline_parse_kernelcore(char *p) > > */ > > static int __init cmdline_parse_movablecore(char *p) > > { > > + pr_warn("Option movablecore= is deprecated.\n"); > > return cmdline_parse_core(p, &required_movablecore, > > &required_movablecore_percent); > > } > > -- > > 2.13.6 > > -- > Michal Hocko > SUSE Labs