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: <ee68b942-492f-4ab9-9341-cd70460812b9@lucifer.local>
Date: Mon, 9 Jun 2025 20:30:05 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.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 Mon, Jun 09, 2025 at 02:34:22PM +0800, Baolin Wang wrote:
>
>
> 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.

Yeah sorry you're right, responded elsewhere in thread.

>
> Thanks for reviewing.

You're welcome!