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

[Andrew Morton]

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