Re: [PATCH v4 0/9] mm: thp: always enable mTHP support

[Luiz Capitulino]

On 2026-05-03 11:02, Andrew Morton wrote:
> On Fri,  1 May 2026 15:18:42 -0400 Luiz Capitulino <luizcap@xxxxxxxxxx> wrote:
>
> > Today, if an architecture implements has_transparent_hugepage() and the CPU
> > lacks support for PMD-sized pages, the THP code disables all THP, including
> > mTHP. In addition, the kernel lacks a well defined API to check for
> > PMD-sized page support. It currently relies on has_transparent_hugepage()
> > and thp_disabled_by_hw(), but they are not well defined and are tied to
> > THP support.
> >
> > This series addresses both issues by introducing a new well defined API
> > to query PMD-sized page support: pgtable_has_pmd_leaves(). Using this
> > new helper, we ensure that mTHP remains enabled even when the
> > architecture or CPU doesn't support PMD-sized pages.
> >
> > Thanks to David Hildenbrand for suggesting this improvement and for
> > providing guidance (all bugs and misconceptions are mine).
> >
> > This applies to Linus tree 08d0d3466664 ("Merge tag 'net-7.1-rc2'
> > of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")
> >
> > NOTE: I used Claude Code Opus 4.6 to *review* the series before
> > posting. It did find one issue where a pgtable_has_pmd_leaves()
> > check was missing when assining huge_shmem_orders_inherit in
> > shmem_init().
>
> Thanks.
>
> Sashiko found a few other things to ask about:
> 	https://sashiko.dev/#/patchset/cover.1777663129.git.luizcap@xxxxxxxxxx

Thanks, I'll go over those soon.