From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@suse.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 19:08:05 +0100 [thread overview]
Message-ID: <5a755ff6-4085-da64-08d5-49dd232029eb@redhat.com> (raw)
In-Reply-To: <YFy8ARml4R7/snVs@dhcp22.suse.cz>
On 25.03.21 17:36, Michal Hocko wrote:
> On Thu 25-03-21 17:20:23, David Hildenbrand wrote:
>> On 25.03.21 17:07, Michal Hocko wrote:
>>> On Thu 25-03-21 16:35:58, Michal Hocko wrote:
>>> [...]
>>>> So there is indeed a difference. One way around that would be to mark
>>>> vmemmap pages (e.g. PageReserved && magic value stored somewhere in the
>>>> struct page - resembling bootmem vmemmaps) or mark section fully backing
>>>> vmemmaps as online (ugly).
>>>
>>> I am not yet ready to give up on this. Here is a quick stab at the
>>> pfn_to_online_page approach. It is not great but it is not really
>>> terrible either. I think we can do better and skip
>>
>> We both seem to have a different taste, to phrase it in a nice way :) ; but
>> well, you seem to have set your mind (just like I seem to have set mine when
>> trying to find a nice and somewhat-clean way to handle this when discussing
>> it in the past).
>
> I definitely do not want to fight for a certain solution just for the
> sake of it. I really dislike how the lifetime of the reserved space and
> its accounting are completely detached. But hey, I do understand that
> a worse solution from the design perspective can be better due to
> practical reasons or constrains.
>
> I haven't seen the hibernation problem before and I do recognize it is
> a nasty one. If all it takes is to make pfn_to_online_page work (and my
> previous attempt is incorrect because it should consult block rather
> than section pfn range) and there are no other downsides then I would
> still prefer to go with my proposal. If there are still other things to
> plug then, well, practicality is going to win.
>
> So before I give up on the "proper" design card, are there more
> subtleties to watch for? You have certainly given this much more thought
> than I have.
>
"Just one more thing" :)
With the pfn_to_online_page() change, I think what remains is
1. The contiguous zone thingy, which we discussed is not a deal breaker,
although sub-optimal and most probably not to be optimized in the future.
2. There corner cases issue with /dev/mem use case with offline memory
blocks I mentioned. Existing setups (!memmap_on_memory) are not
affected, so I guess we're fine.
3. valid_zones_show() has to be taught to only look at the !vmemmap
part, otherwise we'll no longer indicate "movable" after onlining to the
movable zone. Should be fairly easy.
We'll have pfn_to_online_section() succeed without SECTION_IS_ONLINE. I
think I/we removed all such code that purely relied on that flag for
optimizations like
if (!online_section(s))
continue;
I can give it some more thought, it could fly. At least zone shrinking
and hibernation should continue working as expected, which is a relief.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-03-25 18:09 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
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 [this message]
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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