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Subject: Re: [PATCH v1] mm: relax deferred struct page requirements
From:   Jiri Slaby <jslaby@suse.cz>
Cc:     mhocko@kernel.org, Steven Sistare <steven.sistare@oracle.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
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Message-ID: <c4d46b63-5237-d002-faf5-4e0749d825d7@suse.cz>
Date:   Fri, 24 Aug 2018 09:44:40 +0200
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pasha.tatashin@oracle.com -> pavel.tatashin@microsoft.com

due to
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On 08/24/2018, 09:32 AM, Jiri Slaby wrote:
> On 06/19/2018, 09:56 PM, Pavel Tatashin wrote:
>> On Tue, Jun 19, 2018 at 9:50 AM Pavel Tatashin
>> <pasha.tatashin@oracle.com> wrote:
>>>
>>> On Sat, Jun 16, 2018 at 4:04 AM Jiri Slaby <jslaby@suse.cz> wrote:
>>>>
>>>> On 11/21/2017, 08:24 AM, Michal Hocko wrote:
>>>>> On Thu 16-11-17 20:46:01, Pavel Tatashin wrote:
>>>>>> There is no need to have ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT,
>>>>>> as all the page initialization code is in common code.
>>>>>>
>>>>>> Also, there is no need to depend on MEMORY_HOTPLUG, as initialization code
>>>>>> does not really use hotplug memory functionality. So, we can remove this
>>>>>> requirement as well.
>>>>>>
>>>>>> This patch allows to use deferred struct page initialization on all
>>>>>> platforms with memblock allocator.
>>>>>>
>>>>>> Tested on x86, arm64, and sparc. Also, verified that code compiles on
>>>>>> PPC with CONFIG_MEMORY_HOTPLUG disabled.
>>>>>
>>>>> There is slight risk that we will encounter corner cases on some
>>>>> architectures with weird memory layout/topology
>>>>
>>>> Which x86_32-pae seems to be. Many bad page state errors are emitted
>>>> during boot when this patch is applied:
>>>
>>> Hi Jiri,
>>>
>>> Thank you for reporting this bug.
>>>
>>> Because 32-bit systems are limited in the maximum amount of physical
>>> memory, they don't need deferred struct pages. So, we can add depends
>>> on 64BIT to DEFERRED_STRUCT_PAGE_INIT in mm/Kconfig.
>>>
>>> However, before we do this, I want to try reproducing this problem and
>>> root cause it, as it might expose a general problem that is not 32-bit
>>> specific.
>>
>> Hi Jiri,
>>
>> Could you please attach your config and full qemu arguments that you
>> used to reproduce this bug.
> 
> Hi,
> 
> I seem I never replied. Attaching .config and the qemu cmdline:
> $ qemu-kvm -m 2000 -hda /dev/null -kernel bzImage
> 
> "-m 2000" is important to reproduce.
> 
> If I disable CONFIG_DEFERRED_STRUCT_PAGE_INIT (which the patch allowed
> to enable), the error goes away, of course.
> 
> thanks,
> 


-- 
js
suse labs