From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 1837B6B0007 for ; Wed, 10 Oct 2018 02:12:57 -0400 (EDT) Received: by mail-pf1-f197.google.com with SMTP id a64-v6so3782476pfg.16 for ; Tue, 09 Oct 2018 23:12:57 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTPS id z16-v6si23219548plo.5.2018.10.09.23.12.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Oct 2018 23:12:55 -0700 (PDT) Date: Wed, 10 Oct 2018 20:52:12 +0800 From: Yi Zhang Subject: Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Message-ID: <20181010125211.GA45572@tiger-server> References: <20180925200551.3576.18755.stgit@localhost.localdomain> <20180925202053.3576.66039.stgit@localhost.localdomain> <20181009170051.GA40606@tiger-server> <25092df0-b7b4-d456-8409-9c004cb6e422@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: alexander.h.duyck@linux.intel.com, Pasha Tatashin , Michal Hocko , linux-nvdimm , Dave Hansen , Linux Kernel Mailing List , Linux MM , =?utf-8?B?SsOpcsO0bWU=?= Glisse , rppt@linux.vnet.ibm.com, Andrew Morton , Ingo Molnar , "Kirill A. Shutemov" On 2018-10-09 at 14:19:32 -0700, Dan Williams wrote: > On Tue, Oct 9, 2018 at 1:34 PM Alexander Duyck > wrote: > > > > On 10/9/2018 11:04 AM, Dan Williams wrote: > > > On Tue, Oct 9, 2018 at 3:21 AM Yi Zhang wrote: > [..] > > > That comment is incorrect, device-pages are never onlined. So I think > > > we can just skip that call to __SetPageReserved() unless the memory > > > range is MEMORY_DEVICE_{PRIVATE,PUBLIC}. > > > > > > > When pages are "onlined" via __free_pages_boot_core they clear the > > reserved bit, that is the reason for the comment. The reserved bit is > > meant to indicate that the page cannot be swapped out or moved based on > > the description of the bit. > > ...but ZONE_DEVICE pages are never onlined so I would expect > memmap_init_zone_device() to know that detail. > > > I would think with that being the case we still probably need the call > > to __SetPageReserved to set the bit with the expectation that it will > > not be cleared for device-pages since the pages are not onlined. > > Removing the call to __SetPageReserved would probably introduce a number > > of regressions as there are multiple spots that use the reserved bit to > > determine if a page can be swapped out to disk, mapped as system memory, > > or migrated. Another things, it seems page_init/set_reserved already been done in the move_pfn_range_to_zone |-->memmap_init_zone |-->for_each_page_in_pfn |-->__init_single_page |-->SetPageReserved Why we haven't remove these redundant initial in memmap_init_zone? Correct me if I missed something. > > Right, this is what Yi is working on... the PageReserved flag is > problematic for KVM. Auditing those locations it seems as long as we > teach hibernation to avoid ZONE_DEVICE ranges we can safely not set > the reserved flag for DAX pages. What I'm trying to avoid is a local > KVM hack to check for DAX pages when the Reserved flag is not > otherwise needed. Thanks Dan. Provide the patch link. https://lore.kernel.org/lkml/cover.1536342881.git.yi.z.zhang@linux.intel.com > _______________________________________________ > Linux-nvdimm mailing list > Linux-nvdimm@lists.01.org > https://lists.01.org/mailman/listinfo/linux-nvdimm