When an mm with the MMF_DISABLE_THP_COMPLETELY flag is detected during
scanning, directly set khugepaged_scan.mm_slot to the next mm_slot,
reduce redundant operation.

Signed-off-by: Vernon Yang <yanglincheng@kylinos.cn>
---
 mm/khugepaged.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 91836dda2015..a8723eea12f1 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2432,6 +2432,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 
 		cond_resched();
 		if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
+			vma = NULL;
 			progress++;
 			break;
 		}
@@ -2452,8 +2453,10 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 			bool mmap_locked = true;
 
 			cond_resched();
-			if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
+			if (unlikely(hpage_collapse_test_exit_or_disable(mm))) {
+				vma = NULL;
 				goto breakouterloop;
+			}
 
 			VM_BUG_ON(khugepaged_scan.address < hstart ||
 				  khugepaged_scan.address + HPAGE_PMD_SIZE >
@@ -2470,8 +2473,10 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
 				fput(file);
 				if (*result == SCAN_PTE_MAPPED_HUGEPAGE) {
 					mmap_read_lock(mm);
-					if (hpage_collapse_test_exit_or_disable(mm))
+					if (hpage_collapse_test_exit_or_disable(mm)) {
+						vma = NULL;
 						goto breakouterloop;
+					}
 					*result = collapse_pte_mapped_thp(mm,
 						khugepaged_scan.address, false);
 					if (*result == SCAN_PMD_MAPPED)
-- 
2.51.0

On 12/15/25 10:04, Vernon Yang wrote:
> When an mm with the MMF_DISABLE_THP_COMPLETELY flag is detected during
> scanning, directly set khugepaged_scan.mm_slot to the next mm_slot,
> reduce redundant operation.

That conceptually makes sense to me. How much does that safe in 
practice? Do you have some performance numbers for processes with rather 
large number of VMAs?

-- 
Cheers

David

On Thu, Dec 18, 2025 at 10:33:16AM +0100, David Hildenbrand (Red Hat) wrote:
> On 12/15/25 10:04, Vernon Yang wrote:
> > When an mm with the MMF_DISABLE_THP_COMPLETELY flag is detected during
> > scanning, directly set khugepaged_scan.mm_slot to the next mm_slot,
> > reduce redundant operation.
>
> That conceptually makes sense to me. How much does that safe in practice? Do
> you have some performance numbers for processes with rather large number of
> VMAs?

I also only came to this possibility through theoretical analysis and
haven't did any separate performance tests for this patch now.

If you have anything you'd like to test, please let me know, and I can
test the performance benefits.

> --
> Cheers
>
> David

--
Thanks,
Vernon