If a VMA has already created a mapping of large folios after a successful mTHP collapse, we can skip those folios that exceed the 'highest_enabled_order' when scanning the VMA range again, as they can no longer be collapsed further. This helps prevent wasting CPU cycles.
Signed-off-by: Baolin Wang <[email protected]> --- mm/khugepaged.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index a87918b7e18c..a9664ac26f11 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2724,12 +2724,12 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, const unsigned int max_ptes_swap = collapse_max_ptes_swap(cc, HPAGE_PMD_ORDER); struct address_space *mapping = file->f_mapping; XA_STATE(xas, &mapping->i_pages, start); + unsigned int highest_enabled_order = 0; enum scan_result result = SCAN_SUCCEED; unsigned long enabled_orders, nr_pages; struct folio *folio = NULL; int node = NUMA_NO_NODE; int present, swap; - pgoff_t pgoff; present = 0; swap = 0; @@ -2738,6 +2738,9 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, nodes_clear(cc->alloc_nmask); enabled_orders = collapse_possible_orders(vma, vma->vm_flags, tva_flags); + if (enabled_orders > 0) + highest_enabled_order = highest_order(enabled_orders); + /* * If PMD is the only enabled order, enforce max_ptes_none, otherwise * scan all pages to populate the bitmap for mTHP collapse. @@ -2814,10 +2817,17 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, /* * If there are folios present, keep track of it in the bitmap * for file/shmem mTHP collapse. + * + * Skip those folios whose order has already exceeded the + * 'highest_enabled_order', meaning they cannot be collapsed + * into larger order folios. */ - pgoff = max_t(pgoff_t, start, folio->index) - start; - nr_pages = min_t(int, HPAGE_PMD_NR - pgoff, nr_pages); - bitmap_set(cc->mthp_present_ptes, pgoff, nr_pages); + if (folio_order(folio) < highest_enabled_order) { + pgoff_t pgoff = max_t(pgoff_t, start, folio->index) - start; + + nr_pages = min_t(int, HPAGE_PMD_NR - pgoff, nr_pages); + bitmap_set(cc->mthp_present_ptes, pgoff, nr_pages); + } folio_put(folio); @@ -2843,6 +2853,11 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm, goto out; } + if (bitmap_empty(cc->mthp_present_ptes, MAX_PTRS_PER_PTE)) { + result = SCAN_FAIL; + goto out; + } + result = mthp_collapse(mm, file, start, addr, 0, 0, cc, enabled_orders); if (result == SCAN_SUCCEED && !cc->is_khugepaged) { /* If MADV_COLLAPSE, adjust result to call collapse_pte_mapped_thp(). */ -- 2.47.3
