[RFC PATCH 05/12] khugepaged: Generalize __collapse_huge_page_isolate()

Dev Jain
2024-12-16T16:52:33Z

Scale down the scan range and the sysfs tunables according to the scan order,
and isolate the folios.

Signed-off-by: Dev Jain <dev.jain@arm.com>
---
mm/khugepaged.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f52dae7d5179..de044b1f83d4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -564,15 +564,18 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte,
struct collapse_control *cc,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist, int order)
{
- struct page *page = NULL;
- struct folio *folio = NULL;
- pte_t *_pte;
+ unsigned int max_ptes_shared = khugepaged_max_ptes_shared >> (HPAGE_PMD_ORDER - order);
+ unsigned int max_ptes_none = khugepaged_max_ptes_none >> (HPAGE_PMD_ORDER - order);
int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
+ struct folio *folio = NULL;
+ struct page *page = NULL;
bool writable = false;
+ pte_t *_pte;

- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
+
+ for (_pte = pte; _pte < pte + (1UL << order);
_pte++, address += PAGE_SIZE) {
pte_t pteval = ptep_get(_pte);
if (pte_none(pteval) || (pte_present(pteval) &&
@@ -580,7 +583,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
++none_or_zero;
if (!userfaultfd_armed(vma) &&
(!cc->is_khugepaged ||
- none_or_zero <= khugepaged_max_ptes_none)) {
+ none_or_zero <= max_ptes_none)) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
@@ -609,7 +612,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
if (folio_likely_mapped_shared(folio)) {
++shared;
if (cc->is_khugepaged &&
- shared > khugepaged_max_ptes_shared) {
+ shared > max_ptes_shared) {
result = SCAN_EXCEED_SHARED_PTE;
count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
goto out;
@@ -1200,7 +1203,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
if (pte) {
result = __collapse_huge_page_isolate(vma, address, pte, cc,
- &compound_pagelist);
+ &compound_pagelist, order);
spin_unlock(pte_ptl);
} else {
result = SCAN_PMD_NULL;
--
2.30.2