On Wed, Jul 16, 2025 at 9:28 AM David Hildenbrand [off-list ref] wrote:

On 14.07.25 02:32, Nico Pache wrote:

quoted

From: Baolin Wang <baolin.wang@linux.alibaba.com>

Should the subject better be

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

Thank does read better.

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

ehhh, seems like there's a mix of "mm/khugepaged", "khugepaged", and
"mm: khugepaged:" being used in other commits. I prefer using
khugepaged as it leaves me more space for the commit title

quoted

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@linux.alibaba.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
  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 <redacted>

Thank you for your review :)

--
Cheers,

David / dhildenb