linux-kernel - Re: [PATCH v2 2/2] mm: shmem: disallow hugepages if the system-wide shmem THP sysfs settings are disabled

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Message-ID: <aa6aa559-431e-43c0-bd24-828e6558bac3@linux.alibaba.com>
Date: Mon, 9 Jun 2025 14:34:22 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, david@...hat.com,
 Liam.Howlett@...cle.com, npache@...hat.com, ryan.roberts@....com,
 dev.jain@....com, ziy@...dia.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mm: shmem: disallow hugepages if the system-wide
 shmem THP sysfs settings are disabled



On 2025/6/7 20:17, Lorenzo Stoakes wrote:
> On Sat, Jun 07, 2025 at 01:14:41PM +0100, Lorenzo Stoakes wrote:
>> On Thu, Jun 05, 2025 at 04:00:59PM +0800, Baolin Wang wrote:
> [snip]
>>>
>>> Another rule for madvise, referring to David's suggestion: “allowing for collapsing
>>> in a VM without VM_HUGEPAGE in the "madvise" mode would be fine".
>>
>> Hm I'm not sure if this is enforced is it? I may have missed something here
>> however.
> 
> Oh right actually I think it is implicitly - if TVA_ENFORCE_SYSFS is not
> specified in tva_flags, then we don't bother applying an madvise filter at all
> anyway, and we account for that in our 'enabled' check in
> thp_vma_allowable_orders().
> 
> But I don't think this patch changes anything, I actually _think_ we can just
> drop this one.

See my previous replies. Shmem mTHP sysfs settings are different from 
Anonymous pages.

Thanks for reviewing.