Re: [PATCH v13 mm-new 05/16] khugepaged: introduce is_mthp_order helper

Zi Yan
2025-12-03T03:13:50Z

On 1 Dec 2025, at 12:46, Nico Pache wrote:

> In order to add mTHP support, we will often be checking if a given order
> is a mTHP or PMD order. Lets create a simple helper function to keep the
> code clean and readable.
>
> Suggested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Signed-off-by: Nico Pache <npache@redhat.com>
> ---
> mm/khugepaged.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 8599c7fa112e..9c041141b2e3 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -338,6 +338,11 @@ static bool pte_none_or_zero(pte_t pte)
> return pte_present(pte) && is_zero_pfn(pte_pfn(pte));
> }
>
> +static bool is_mthp_order(unsigned int order)
> +{
> + return order != HPAGE_PMD_ORDER;
> +}
> +

The code at the bottom of __folio_split() in mm/huge_memory.c
can use this helper.

The code in deferred_split_folio() uses folio_test_pmd_mappable()
instead of order == HPAGE_PMD_ORDER, but the code can be changed
to use the helper.

> int hugepage_madvise(struct vm_area_struct *vma,
> vm_flags_t *vm_flags, int advice)
> {
> @@ -1071,13 +1076,13 @@ static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
> if (!folio) {
> *foliop = NULL;
> - if (order == HPAGE_PMD_ORDER)
> + if (!is_mthp_order(order))
> count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
> return SCAN_ALLOC_HUGE_PAGE_FAIL;
> }
>
> - if (order == HPAGE_PMD_ORDER)
> + if (!is_mthp_order(order))
> count_vm_event(THP_COLLAPSE_ALLOC);
> count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC);
>
> --
> 2.51.1

Best Regards,
Yan, Zi