From: Michal Hocko <mhocko@suse.com>
To: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Vlastimil Babka <vbabka@suse.cz>,
Pavel Tatashin <pasha.tatashin@soleen.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range
Date: Thu, 25 Mar 2021 15:34:28 +0100 [thread overview]
Message-ID: <YFyfdDAoWON6IoPL@dhcp22.suse.cz> (raw)
In-Reply-To: <062bc5d7-a83c-1c1a-7b77-9f043643f4fa@redhat.com>
On Thu 25-03-21 15:09:35, David Hildenbrand wrote:
> On 25.03.21 15:08, Michal Hocko wrote:
> > On Thu 25-03-21 13:40:45, David Hildenbrand wrote:
> > > On 25.03.21 13:35, Michal Hocko wrote:
> > > > On Thu 25-03-21 12:08:43, David Hildenbrand wrote:
> > > > > On 25.03.21 11:55, Oscar Salvador wrote:
> > [...]
> > > > > > - When moving the initialization/accounting to hot-add/hot-remove,
> > > > > > the section containing the vmemmap pages will remain offline.
> > > > > > It might get onlined once the pages get online in online_pages(),
> > > > > > or not if vmemmap pages span a whole section.
> > > > > > I remember (but maybe David rmemeber better) that that was a problem
> > > > > > wrt. pfn_to_online_page() and hybernation/kdump.
> > > > > > So, if that is really a problem, we would have to care of ot setting
> > > > > > the section to the right state.
> > > > >
> > > > > Good memory. Indeed, hibernation/kdump won't save the state of the vmemmap,
> > > > > because the memory is marked as offline and, thus, logically without any
> > > > > valuable content.
^^^^ THIS
> > > >
> > > > Could you point me to the respective hibernation code please? I always
> > > > get lost in that area. Anyway, we do have the same problem even if the
> > > > whole accounting is handled during {on,off}lining, no?
> > >
> > > kernel/power/snapshot.c:saveable_page().
> >
> > Thanks! So this is as I've suspected. The very same problem is present
> > if the memory block is marked offline. So we need a solution here
> > anyway. One way to go would be to consider these vmemmap pages always
> > online. pfn_to_online_page would have to special case them but we would
> > need to identify them first. I used to have PageVmemmap or something
> > like that in my early attempt to do this.
> >
> > That being said this is not an argument for one or the other aproach.
> > Both need fixing.
>
> Can you elaborate? What is the issue there? What needs fixing?
offline section containing vmemmap will be lost during hibernation cycle
IIU the above correctly.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-25 14:34 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 9:26 [PATCH v5 0/5] Allocate memmap from hotadded memory (per device) Oscar Salvador
2021-03-19 9:26 ` [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range Oscar Salvador
2021-03-19 10:20 ` David Hildenbrand
2021-03-19 10:31 ` Oscar Salvador
2021-03-19 12:04 ` David Hildenbrand
2021-03-23 10:11 ` Michal Hocko
2021-03-24 10:12 ` Oscar Salvador
2021-03-24 12:03 ` Michal Hocko
2021-03-24 12:10 ` Michal Hocko
2021-03-24 12:23 ` David Hildenbrand
2021-03-24 12:37 ` Michal Hocko
2021-03-24 13:13 ` David Hildenbrand
2021-03-24 13:40 ` Michal Hocko
2021-03-24 14:05 ` David Hildenbrand
2021-03-24 13:27 ` Oscar Salvador
2021-03-24 14:42 ` Michal Hocko
2021-03-24 14:52 ` David Hildenbrand
2021-03-24 16:04 ` Michal Hocko
2021-03-24 19:16 ` David Hildenbrand
2021-03-25 8:07 ` Oscar Salvador
2021-03-25 9:17 ` Michal Hocko
2021-03-25 10:55 ` Oscar Salvador
2021-03-25 11:08 ` David Hildenbrand
2021-03-25 11:23 ` Oscar Salvador
2021-03-25 12:35 ` Michal Hocko
2021-03-25 12:40 ` David Hildenbrand
2021-03-25 14:08 ` Michal Hocko
2021-03-25 14:09 ` David Hildenbrand
2021-03-25 14:34 ` Michal Hocko [this message]
2021-03-25 14:46 ` David Hildenbrand
2021-03-25 15:12 ` Michal Hocko
2021-03-25 15:19 ` David Hildenbrand
2021-03-25 15:35 ` Michal Hocko
2021-03-25 15:40 ` David Hildenbrand
2021-03-25 16:07 ` Michal Hocko
2021-03-25 16:20 ` David Hildenbrand
2021-03-25 16:36 ` Michal Hocko
2021-03-25 16:47 ` Michal Hocko
2021-03-25 16:55 ` David Hildenbrand
2021-03-25 22:06 ` Oscar Salvador
2021-03-26 8:35 ` Michal Hocko
2021-03-26 8:52 ` David Hildenbrand
2021-03-26 8:57 ` Oscar Salvador
2021-03-26 12:15 ` Oscar Salvador
2021-03-26 13:36 ` David Hildenbrand
2021-03-26 14:38 ` Michal Hocko
2021-03-26 14:53 ` David Hildenbrand
2021-03-26 15:31 ` Michal Hocko
2021-03-26 16:03 ` David Hildenbrand
2021-03-26 8:55 ` Oscar Salvador
2021-03-26 9:11 ` Michal Hocko
2021-03-25 18:08 ` David Hildenbrand
2021-03-25 12:26 ` Michal Hocko
2021-03-25 14:02 ` Oscar Salvador
2021-03-25 14:40 ` Michal Hocko
2021-03-19 9:26 ` [PATCH v5 2/5] acpi,memhotplug: Enable MHP_MEMMAP_ON_MEMORY when supported Oscar Salvador
2021-03-23 10:40 ` Michal Hocko
2021-03-19 9:26 ` [PATCH v5 3/5] mm,memory_hotplug: Add kernel boot option to enable memmap_on_memory Oscar Salvador
2021-03-23 10:47 ` Michal Hocko
2021-03-24 8:45 ` Oscar Salvador
2021-03-24 9:02 ` Michal Hocko
2021-03-19 9:26 ` [PATCH v5 4/5] x86/Kconfig: Introduce ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE Oscar Salvador
2021-03-19 9:26 ` [PATCH v5 5/5] arm64/Kconfig: " Oscar Salvador
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