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ZEJyKTDit8Offoo+KWoUPTNj1j4ABVcEYH6pOngU5JqirBLJPjy4eFuqfYe9g1xCG4qRhv39a6NXQSH5tr++oz4Gdb+xlRSfeG/f6fQWwSESxRXT3L2wupaqsRPU3bmYCgfK5BFBPulzDOnful0HJOLB228/nx6yZA3buECu0qHjxs/Rv8lwV4ns9UbzNCSKrWZ/LDsoyfr1f850neexyfUqL5ikfnC7WgiMtm5RgrDnnR9h/GAKs0vNoss0iqZ129h6c4Jqxc0T/gMLGcSh2g78yLrFQ2jfedMpu1jLersSTMvQQrD9ZlcQKHMm3IUGGGgMxLHttpYVjQzVHVFDKJE76enXVKvraLKpKG/825zjs5Rl6pxi2GI9JfFiomDZPeF7UNI6Q8DdG6sxzg+G9rSnORz4idSII2xQ8 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9 Apr 2026, at 16:07, Luiz Capitulino wrote: > On 2026-04-09 11:55, Zi Yan wrote: >> On 8 Apr 2026, at 16:23, Luiz Capitulino wrote: >> >>> If PMD-sized pages are not supported on an architecture (ie. the >>> arch implements arch_has_pmd_leaves() and it returns false) then the >>> current code disables all THP, including mTHP. >>> >>> This commit fixes this by allowing mTHP to be always enabled for all >>> archs. When PMD-sized pages are not supported, its sysfs entry won't be >>> created and their mapping will be disallowed at page-fault time. >>> >>> Similarly, this commit implements the following changes for shmem: >>> >>> - In shmem_allowable_huge_orders(): drop the pgtable_has_pmd_leaves() >>> check so that mTHP sizes are considered >>> - In shmem_alloc_and_add_folio(): don't consider PMD and PUD orders >>> when PMD-sized pages are not supported by the CPU >>> >>> Signed-off-by: Luiz Capitulino >>> --- >>> mm/huge_memory.c | 13 ++++++++----- >>> mm/shmem.c | 4 +++- >>> 2 files changed, 11 insertions(+), 6 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 86e489c0a150..6de3d8ebc35c 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -118,6 +118,9 @@ unsigned long __thp_vma_allowable_orders(struct vm_= area_struct *vma, >>> else >>> supported_orders =3D THP_ORDERS_ALL_FILE_DEFAULT; >>> >>> + if (!pgtable_has_pmd_leaves()) >>> + supported_orders &=3D ~(BIT(PMD_ORDER) | BIT(PUD_ORDER)); >> >> Why is BIT(PUD_ORDER) also removed? I thought PMD THP support and PUD TH= P support >> are separate. Here the code implies PUD THP relies on PMD THP. Is that t= he case? > > This was a suggestion from David to an earlier version: > > https://lore.kernel.org/linux-mm/dac20466-adac-4e47-8f50-87f4774fd57b@ker= nel.org/ > > My understanding was that if an arch doesn't support PMD pages then it > probably doesn't support PUD pages either. Got it. Can you add a comment on =E2=80=9CNo PMD leaves -> No PUD leaves=E2= =80=9D for pgtable_has_pmd_leaves(), so that no one would ask the same question again? Thanks. Best Regards, Yan, Zi