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From: Yi Zhang <yi.z.zhang@linux.intel.com>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: "Pasha Tatashin" <pavel.tatashin@microsoft.com>,
	"Michal Hocko" <mhocko@suse.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Ingo Molnar" <mingo@kernel.org>, "Linux MM" <linux-mm@kvack.org>,
	"Dave Hansen" <dave.hansen@intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	rppt@linux.vnet.ibm.com,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap
Date: Thu, 11 Oct 2018 16:17:54 +0800	[thread overview]
Message-ID: <20181011081754.GA51021@tiger-server> (raw)
In-Reply-To: <deb1264e-5a42-3467-9073-e829b8eab8ca@linux.intel.com>

On 2018-10-10 at 08:27:58 -0700, Alexander Duyck wrote:
> 
> 
> On 10/10/2018 5:52 AM, Yi Zhang wrote:
> >On 2018-10-09 at 14:19:32 -0700, Dan Williams wrote:
> >>On Tue, Oct 9, 2018 at 1:34 PM Alexander Duyck
> >><alexander.h.duyck@linux.intel.com> wrote:
> >>>
> >>>On 10/9/2018 11:04 AM, Dan Williams wrote:
> >>>>On Tue, Oct 9, 2018 at 3:21 AM Yi Zhang <yi.z.zhang@linux.intel.com> 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.
> 
> In this case it isn't redundant as only the vmmemmap pages are initialized
> in memmap_init_zone now. So all of the pages that are going to be used as
> device pages are not initialized until the call to memmap_init_zone_device.
> What I did is split the initialization of the pages into two parts in order
> to allow us to initialize the pages outside of the hotplug lock.
Ah.. I saw that, Thanks the explanation, so that is we only need to
care about the device pages reserved flag, and plan to remove that.
> 
> >>
> >>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
> 
> So it looks like your current logic is just working around the bit then
> since it just allows for reserved DAX pages.
> 
> 
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  reply	other threads:[~2018-10-11  1:39 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-25 20:18 [PATCH v5 0/4] Address issues slowing persistent memory initialization Alexander Duyck
2018-09-25 20:19 ` [PATCH v5 1/4] mm: Remove now defunct NO_BOOTMEM from depends list for deferred init Alexander Duyck
2018-09-25 21:05   ` Mike Rapoport
2018-09-25 20:20 ` [PATCH v5 2/4] mm: Provide kernel parameter to allow disabling page init poisoning Alexander Duyck
2018-09-25 20:26   ` Dave Hansen
2018-09-25 20:38     ` Alexander Duyck
2018-09-25 22:14       ` Dave Hansen
2018-09-25 22:27         ` Alexander Duyck
2018-09-26  7:38   ` Michal Hocko
2018-09-26 15:24     ` Alexander Duyck
2018-09-26 15:39       ` Michal Hocko
2018-09-26 15:41       ` Dave Hansen
2018-09-26 16:18         ` Alexander Duyck
2018-09-26 15:36     ` Dave Hansen
2018-09-26 22:36       ` Andrew Morton
2018-09-25 20:20 ` [PATCH v5 3/4] mm: Create non-atomic version of SetPageReserved for init use Alexander Duyck
2018-09-25 20:21 ` [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Alexander Duyck
2018-09-26  7:55   ` Michal Hocko
2018-09-26 18:25     ` Alexander Duyck
2018-09-26 18:52       ` Dan Williams
2018-09-27 11:20         ` Michal Hocko
2018-09-27 11:09       ` Michal Hocko
2018-09-27 12:25         ` Oscar Salvador
2018-09-27 13:13           ` Michal Hocko
2018-09-27 14:50             ` Oscar Salvador
2018-09-27 15:41               ` David Hildenbrand
2018-09-28  8:12             ` Oscar Salvador
2018-09-28  8:44               ` Oscar Salvador
2018-09-28 15:50                 ` Dan Williams
2018-09-27 12:32       ` Oscar Salvador
2018-10-08 21:01   ` Dan Williams
2018-10-08 21:38     ` Alexander Duyck
2018-10-08 22:00       ` Dan Williams
2018-10-08 22:07         ` Alexander Duyck
2018-10-08 22:36         ` Alexander Duyck
2018-10-08 22:59           ` Dan Williams
2018-10-08 23:34     ` [mm PATCH] memremap: Fix reference count for pgmap in devm_memremap_pages Alexander Duyck
2018-10-09  0:20       ` Dan Williams
2018-10-09 17:00   ` [PATCH v5 4/4] mm: Defer ZONE_DEVICE page initialization to the point where we init pgmap Yi Zhang
2018-10-09 18:04     ` Dan Williams
2018-10-09 20:26       ` Alexander Duyck
2018-10-09 21:19         ` Dan Williams
2018-10-10 12:52           ` Yi Zhang
2018-10-10 15:27             ` Alexander Duyck
2018-10-11  8:17               ` Yi Zhang [this message]
2018-10-10  9:58         ` Michal Hocko
2018-10-10 16:39           ` Alexander Duyck
2018-10-10 17:24             ` Michal Hocko
2018-10-10 17:39               ` Alexander Duyck
2018-10-10 17:53                 ` Michal Hocko
2018-10-10 18:13                   ` Alexander Duyck
2018-10-10 18:52                 ` Michal Hocko
2018-10-11  8:55                   ` Michal Hocko
2018-10-11 17:38                     ` Alexander Duyck
2018-10-11 18:22                       ` Dan Williams
2018-10-17  7:52                       ` Michal Hocko
2018-10-17 15:02                         ` Alexander Duyck
2018-10-29 14:12                           ` Michal Hocko
2018-10-29 15:59                             ` Alexander Duyck
2018-10-29 16:35                               ` Michal Hocko
2018-10-29 17:01                                 ` Alexander Duyck
2018-10-29 17:24                                   ` Michal Hocko
2018-10-29 17:34                                     ` Dan Williams
2018-10-29 17:45                                       ` Michal Hocko
2018-10-29 17:42                                     ` Alexander Duyck
2018-10-29 18:18                                       ` Michal Hocko
2018-10-29 19:59                                         ` Alexander Duyck
2018-10-30  6:29                                           ` Michal Hocko
2018-10-30  6:55                                             ` Dan Williams
2018-10-30  8:17                                               ` Michal Hocko
2018-10-30 15:57                                                 ` Dan Williams
2018-10-30  8:05                                           ` Oscar Salvador
2018-10-29 15:49                           ` Dan Williams
2018-10-29 15:56                             ` Michal Hocko
2018-10-10 18:18               ` Dan Williams
2018-10-11  8:39                 ` Yi Zhang
2018-10-11 15:38                   ` Alexander Duyck

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