Re: [PATCH v9 10/14] khugepaged: allow khugepaged to check all anonymous mTHP orders

[David Hildenbrand]

On 14.07.25 02:32, Nico Pache wrote:
> From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>

Should the subject better be

"mm/khugepaged: enable collapsing mTHPs even when PMD THPs are disabled"

(in general, I assume all subjects should be prefixed by "mm/khugepaged:")

> We have now allowed mTHP collapse, but thp_vma_allowable_order() still only
> checks if the PMD-sized mTHP is allowed to collapse. This prevents scanning
> and collapsing of 64K mTHP when only 64K mTHP is enabled. Thus, we should
> modify the checks to allow all large orders of anonymous mTHP.
>
> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Nico Pache <npache@xxxxxxxxxx>
> ---
>   mm/khugepaged.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 7a9c4edf0e23..3772dc0d78ea 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -491,8 +491,11 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
>   {
>   	if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
>   	    hugepage_pmd_enabled()) {
> -		if (thp_vma_allowable_order(vma, vm_flags, TVA_ENFORCE_SYSFS,
> -					    PMD_ORDER))
> +		unsigned long orders = vma_is_anonymous(vma) ?
> +					THP_ORDERS_ALL_ANON : BIT(PMD_ORDER);
> +
> +		if (thp_vma_allowable_orders(vma, vm_flags, TVA_ENFORCE_SYSFS,
> +					    orders))
>   			__khugepaged_enter(vma->vm_mm);
>   	}
>   }
> @@ -2624,6 +2627,8 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result,
>   
>   	vma_iter_init(&vmi, mm, khugepaged_scan.address);
>   	for_each_vma(vmi, vma) {
> +		unsigned long orders = vma_is_anonymous(vma) ?
> +					THP_ORDERS_ALL_ANON : BIT(PMD_ORDER);
>   		unsigned long hstart, hend;
>   
>   		cond_resched();
> @@ -2631,8 +2636,8 @@ static unsigned int collapse_scan_mm_slot(unsigned int pages, int *result,
>   			progress++;
>   			break;
>   		}
> -		if (!thp_vma_allowable_order(vma, vma->vm_flags,
> -					TVA_ENFORCE_SYSFS, PMD_ORDER)) {
> +		if (!thp_vma_allowable_orders(vma, vma->vm_flags,
> +			TVA_ENFORCE_SYSFS, orders)) {
>   skip:
>   			progress++;
>   			continue;

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb