linux-kernel - RE: slow boot with 7fef431be9c9 ("mm/page_alloc: place pages to tail in __free_pages

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Message-ID: <MW3PR12MB453771424C9B2866BBBAE036F36B9@MW3PR12MB4537.namprd12.prod.outlook.com>
Date:   Tue, 16 Mar 2021 08:43:12 +0000
From:   "Liang, Liang (Leo)" <Liang.Liang@....com>
To:     David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>
CC:     "Deucher, Alexander" <Alexander.Deucher@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Huang, Ray" <Ray.Huang@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        George Kennedy <george.kennedy@...cle.com>
Subject: RE: slow boot with 7fef431be9c9 ("mm/page_alloc: place pages to tail
 in __free_pages_core()")

[AMD Public Use]

Hi David,

Thanks for your explanation. We saw slow boot issue on our farm/QA's machines and mine. All of machines are same SoC/board.

BRs,
Leo
-----Original Message-----
From: David Hildenbrand <david@...hat.com> 
Sent: Tuesday, March 16, 2021 4:38 PM
To: Liang, Liang (Leo) <Liang.Liang@....com>; Mike Rapoport <rppt@...ux.ibm.com>
Cc: Deucher, Alexander <Alexander.Deucher@....com>; linux-kernel@...r.kernel.org; amd-gfx list <amd-gfx@...ts.freedesktop.org>; Andrew Morton <akpm@...ux-foundation.org>; Huang, Ray <Ray.Huang@....com>; Koenig, Christian <Christian.Koenig@....com>; Rafael J. Wysocki <rafael@...nel.org>; George Kennedy <george.kennedy@...cle.com>
Subject: Re: slow boot with 7fef431be9c9 ("mm/page_alloc: place pages to tail in __free_pages_core()")

On 16.03.21 09:00, Liang, Liang (Leo) wrote:
> [AMD Public Use]
> 
> Hi Mike,
> 
> Thanks for help. The patch works for me and boot time back to normal. So it's a fix, or just WA?

Hi Leo,

excluding up to 16 MiB of memory on every system just because that single platform is weird is not acceptable.

I think we have to figure out

a) why that memory is so special. This is weird.
b) why the platform doesn't indicate it in a special way. Why is it ordinary system RAM but still *that* slow?
c) how we can reliably identify such memory and exclude it.

I'll have a peek at the memory layout of that machine from boot logs next to figure out if we can answer any of these questions.

Just to verify: this does happen on multiple machines, not just a single one? (i.e., we're not dealing with faulty RAM)

--
Thanks,

David / dhildenb