Re: [PATCH v8 14/15] khugepaged: add per-order mTHP khugepaged stats

On Tue, Jul 8, 2025 at 12:10 AM Baolin Wang
[off-list ref] wrote:

On 2025/7/2 13:57, Nico Pache wrote:

quoted

With mTHP support inplace, let add the per-order mTHP stats for
exceeding NONE, SWAP, and SHARED.

Signed-off-by: Nico Pache <redacted>
---
  include/linux/huge_mm.h |  3 +++
  mm/huge_memory.c        |  7 +++++++
  mm/khugepaged.c         | 15 ++++++++++++---
  3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a6ea89fdaee6..6034b4c9dae5 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h

@@ -141,6 +141,9 @@ enum mthp_stat_item {
      MTHP_STAT_SPLIT_DEFERRED,
      MTHP_STAT_NR_ANON,
      MTHP_STAT_NR_ANON_PARTIALLY_MAPPED,
+     MTHP_STAT_COLLAPSE_EXCEED_SWAP,

This stat seems never used.

Ah good catch, I somehow dropped that piece on the V5->v6/7

quoted

+     MTHP_STAT_COLLAPSE_EXCEED_NONE,
+     MTHP_STAT_COLLAPSE_EXCEED_SHARED,
      __MTHP_STAT_COUNT
  };

Please also update the 'Documentation/admin-guide/mm/transhuge.rst' for
these new statistics.

Will do thanks :)

quoted

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 69777a35e722..3eb1c34be601 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c

@@ -632,6 +632,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
  DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
  DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
  DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_swap_pte, MTHP_STAT_COLLAPSE_EXCEED_SWAP);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_none_pte, MTHP_STAT_COLLAPSE_EXCEED_NONE);
+DEFINE_MTHP_STAT_ATTR(collapse_exceed_shared_pte, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+

  static struct attribute *anon_stats_attrs[] = {
      &anon_fault_alloc_attr.attr,

@@ -648,6 +652,9 @@ static struct attribute *anon_stats_attrs[] = {
      &split_deferred_attr.attr,
      &nr_anon_attr.attr,
      &nr_anon_partially_mapped_attr.attr,
+     &collapse_exceed_swap_pte_attr.attr,
+     &collapse_exceed_none_pte_attr.attr,
+     &collapse_exceed_shared_pte_attr.attr,
      NULL,
  };

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2c0962637c34..636b84bf1ca1 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c

@@ -594,7 +594,10 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
                              continue;
                      } else {
                              result = SCAN_EXCEED_NONE_PTE;
-                             count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+                             if (order == HPAGE_PMD_ORDER)
+                                     count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
+                             else
+                                     count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE);
                              goto out;
                      }
              }

@@ -623,8 +626,14 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
              /* See khugepaged_scan_pmd(). */
              if (folio_maybe_mapped_shared(folio)) {
                      ++shared;
-                     if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&
-                         shared > khugepaged_max_ptes_shared)) {
+                     if (order != HPAGE_PMD_ORDER) {
+                             result = SCAN_EXCEED_SHARED_PTE;
+                             count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED);
+                             goto out;
+                     }
+
+                     if (cc->is_khugepaged &&
+                             shared > khugepaged_max_ptes_shared) {
                              result = SCAN_EXCEED_SHARED_PTE;
                              count_vm_event(THP_SCAN_EXCEED_SHARED_PTE);
                              goto out;