On 3/3/26 03:36, Baolin Wang wrote:

On 3/2/26 5:07 PM, David Hildenbrand (Arm) wrote:

quoted

On 2/27/26 10:44, Baolin Wang wrote:

quoted

Currently, MGLRU will call ptep_test_and_clear_young_notify() to
check and
clear the young flag for each PTE sequentially, which is inefficient for
large folios reclamation.

Moreover, on Arm64 architecture, which supports contiguous PTEs, the
Arm64-
specific ptep_test_and_clear_young() already implements an
optimization to
clear the young flags for PTEs within a contiguous range. However,
this is not
sufficient. Similar to the Arm64 specific clear_flush_young_ptes(),
we can
extend this to perform batched operations for the entire large folio
(which
might exceed the contiguous range: CONT_PTE_SIZE).

Thus, we can introduce a new batched helper:
test_and_clear_young_ptes() and
its wrapper test_and_clear_young_ptes_notify() which are consistent
with the
existing functions, to perform batched checking of the young flags
for large
folios, which can help improve performance during large folio
reclamation when
MGLRU is enabled. And it will be overridden by the architecture that
implements
a more efficient batch operation in the following patches.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
  include/linux/pgtable.h | 38 ++++++++++++++++++++++++++++++++++++++
  mm/internal.h           | 16 +++++++++++-----
  2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 776993d4567b..29bd9fd04e1e 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h

@@ -1103,6 +1103,44 @@ static inline int

clear_flush_young_ptes(struct vm_area_struct *vma,
  }
  #endif
  +#ifndef test_and_clear_young_ptes
+/**
+ * test_and_clear_young_ptes - Mark PTEs that map consecutive pages
of the same
+ *                   folio as old
+ * @vma: The virtual memory area the pages are mapped into.
+ * @addr: Address the first page is mapped at.
+ * @ptep: Page table pointer for the first entry.
+ * @nr: Number of entries to clear access bit.
+ *
+ * May be overridden by the architecture; otherwise, implemented as
a simple
+ * loop over ptep_test_and_clear_young().
+ *
+ * Note that PTE bits in the PTE range besides the PFN can differ.
For example,
+ * some PTEs might be write-protected.
+ *
+ * Context: The caller holds the page table lock.  The PTEs map
consecutive
+ * pages that belong to the same folio.  The PTEs are all in the
same PMD.
+ *
+ * Returns: whether any PTE was young.
+ */
+static inline int test_and_clear_young_ptes(struct vm_area_struct *vma,
+                        unsigned long addr, pte_t *ptep,
+                        unsigned int nr)

Two tabs ...

Ah, yes, not sure why I missed this one :(

quoted

What happened to using a boolen as return type and for "int young"?

As I replied to you previously [1], I’d like to do this in a follow-up
patchset that converts all functions that check the young flag. Does
that sound OK to you?

[1] https://lore.kernel.org/all/32c538ce-6af8-48a8-86fc-
d26ee253af54@linux.alibaba.com/

Oh, missed that. Works for me.

-- 
Cheers,

David