On Tue, Aug 26, 2025 at 3:43 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
[...]
> @@ -4510,13 +4510,18 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf)
> if (!zswap_never_enabled())
> goto fallback;
>
> + suggested_orders = get_suggested_order(vma->vm_mm, vma, vma->vm_flags,
> + TVA_PAGEFAULT,
> + BIT(PMD_ORDER) - 1);
Can we separate this case from the normal anonymous page faults below?
We’ve observed that swapping in large folios can lead to more
swap thrashing for some workloads- e.g. kernel build. Consequently,
some workloads
might prefer swapping in smaller folios than those allocated by
alloc_anon_folio().
> + if (!suggested_orders)
> + goto fallback;
> entry = pte_to_swp_entry(vmf->orig_pte);
> /*
> * Get a list of all the (large) orders below PMD_ORDER that are enabled
> * and suitable for swapping THP.
> */
> orders = thp_vma_allowable_orders(vma, vma->vm_flags, TVA_PAGEFAULT,
> - BIT(PMD_ORDER) - 1);
> + suggested_orders);
> orders = thp_vma_suitable_orders(vma, vmf->address, orders);
> orders = thp_swap_suitable_orders(swp_offset(entry),
> vmf->address, orders);
> @@ -5044,12 +5049,12 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
> {
> struct vm_area_struct *vma = vmf->vma;
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> + int order, suggested_orders;
> unsigned long orders;
> struct folio *folio;
> unsigned long addr;
> pte_t *pte;
> gfp_t gfp;
> - int order;
>
> /*
> * If uffd is active for the vma we need per-page fault fidelity to
> @@ -5058,13 +5063,18 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
> if (unlikely(userfaultfd_armed(vma)))
> goto fallback;
>
> + suggested_orders = get_suggested_order(vma->vm_mm, vma, vma->vm_flags,
> + TVA_PAGEFAULT,
> + BIT(PMD_ORDER) - 1);
> + if (!suggested_orders)
> + goto fallback;
Thanks
Barry
