Barry Song <21cnbao@xxxxxxxxx> writes:
> From: Chuanhua Han <hanchuanhua@xxxxxxxx>
>
> When a large folio is found in the swapcache, the current implementation
> requires calling do_swap_page() nr_pages times, resulting in nr_pages
> page faults. This patch opts to map the entire large folio at once to
> minimize page faults. Additionally, redundant checks and early exits
> for ARM64 MTE restoring are removed.
>
> Signed-off-by: Chuanhua Han <hanchuanhua@xxxxxxxx>
> Co-developed-by: Barry Song <v-songbaohua@xxxxxxxx>
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
> Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
LGTM, Thanks! Feel free to add
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
in the future version.
> ---
> mm/memory.c | 59 +++++++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 48 insertions(+), 11 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index d9434df24d62..8b9e4cab93ed 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3968,6 +3968,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> pte_t pte;
> vm_fault_t ret = 0;
> void *shadow = NULL;
> + int nr_pages;
> + unsigned long page_idx;
> + unsigned long address;
> + pte_t *ptep;
>
> if (!pte_unmap_same(vmf))
> goto out;
> @@ -4166,6 +4170,38 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> goto out_nomap;
> }
>
> + nr_pages = 1;
> + page_idx = 0;
> + address = vmf->address;
> + ptep = vmf->pte;
> + if (folio_test_large(folio) && folio_test_swapcache(folio)) {
> + int nr = folio_nr_pages(folio);
> + unsigned long idx = folio_page_idx(folio, page);
> + unsigned long folio_start = address - idx * PAGE_SIZE;
> + unsigned long folio_end = folio_start + nr * PAGE_SIZE;
> + pte_t *folio_ptep;
> + pte_t folio_pte;
> +
> + if (unlikely(folio_start < max(address & PMD_MASK, vma->vm_start)))
> + goto check_folio;
> + if (unlikely(folio_end > pmd_addr_end(address, vma->vm_end)))
> + goto check_folio;
> +
> + folio_ptep = vmf->pte - idx;
> + folio_pte = ptep_get(folio_ptep);
> + if (!pte_same(folio_pte, pte_move_swp_offset(vmf->orig_pte, -idx)) ||
> + swap_pte_batch(folio_ptep, nr, folio_pte) != nr)
> + goto check_folio;
> +
> + page_idx = idx;
> + address = folio_start;
> + ptep = folio_ptep;
> + nr_pages = nr;
> + entry = folio->swap;
> + page = &folio->page;
> + }
> +
> +check_folio:
> /*
> * PG_anon_exclusive reuses PG_mappedtodisk for anon pages. A swap pte
> * must never point at an anonymous page in the swapcache that is
> @@ -4225,12 +4261,12 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> * We're already holding a reference on the page but haven't mapped it
> * yet.
> */
> - swap_free(entry);
> + swap_free_nr(entry, nr_pages);
> if (should_try_to_free_swap(folio, vma, vmf->flags))
> folio_free_swap(folio);
>
> - inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
> - dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
> + add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages);
> + add_mm_counter(vma->vm_mm, MM_SWAPENTS, -nr_pages);
> pte = mk_pte(page, vma->vm_page_prot);
>
> /*
> @@ -4247,27 +4283,28 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> }
> rmap_flags |= RMAP_EXCLUSIVE;
> }
> - flush_icache_page(vma, page);
> + folio_ref_add(folio, nr_pages - 1);
> + flush_icache_pages(vma, page, nr_pages);
> if (pte_swp_soft_dirty(vmf->orig_pte))
> pte = pte_mksoft_dirty(pte);
> if (pte_swp_uffd_wp(vmf->orig_pte))
> pte = pte_mkuffd_wp(pte);
> - vmf->orig_pte = pte;
> + vmf->orig_pte = pte_advance_pfn(pte, page_idx);
>
> /* ksm created a completely new copy */
> if (unlikely(folio != swapcache && swapcache)) {
> - folio_add_new_anon_rmap(folio, vma, vmf->address);
> + folio_add_new_anon_rmap(folio, vma, address);
> folio_add_lru_vma(folio, vma);
> } else {
> - folio_add_anon_rmap_pte(folio, page, vma, vmf->address,
> + folio_add_anon_rmap_ptes(folio, page, nr_pages, vma, address,
> rmap_flags);
> }
>
> VM_BUG_ON(!folio_test_anon(folio) ||
> (pte_write(pte) && !PageAnonExclusive(page)));
> - set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
> - arch_do_swap_page_nr(vma->vm_mm, vma, vmf->address,
> - pte, vmf->orig_pte, 1);
> + set_ptes(vma->vm_mm, address, ptep, pte, nr_pages);
> + arch_do_swap_page_nr(vma->vm_mm, vma, address,
> + pte, pte, nr_pages);
>
> folio_unlock(folio);
> if (folio != swapcache && swapcache) {
> @@ -4291,7 +4328,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> }
>
> /* No need to invalidate - it was non-present before */
> - update_mmu_cache_range(vmf, vma, vmf->address, vmf->pte, 1);
> + update_mmu_cache_range(vmf, vma, address, ptep, nr_pages);
> unlock:
> if (vmf->pte)
> pte_unmap_unlock(vmf->pte, vmf->ptl);
--
Best Regards,
Huang, Ying
