From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: "Dan Williams" <dan.j.williams@intel.com>,
"Pasha Tatashin" <pavel.tatashin@microsoft.com>,
"Michal Hocko" <mhocko@suse.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
"Dave Hansen" <dave.hansen@intel.com>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Linux MM" <linux-mm@kvack.org>,
"Jérôme Glisse" <jglisse@redhat.com>,
rppt@linux.vnet.ibm.com,
"Andrew Morton" <akpm@linux-foundation.org>,
"Ingo Molnar" <mingo@kernel.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: Wed, 10 Oct 2018 08:27:58 -0700 [thread overview]
Message-ID: <deb1264e-5a42-3467-9073-e829b8eab8ca@linux.intel.com> (raw)
In-Reply-To: <20181010125211.GA45572@tiger-server>
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.
>>
>> 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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next prev parent reply other threads:[~2018-10-10 15:28 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 [this message]
2018-10-11 8:17 ` Yi Zhang
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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