Re: [PATCH v12 mm-new 04/15] khugepaged: generalize alloc_charge_folio()

[Lance Yang]

On 2025/10/23 02:37, Nico Pache wrote:

From: Dev Jain <dev.j...@arm.com>

Pass order to alloc_charge_folio() and update mTHP statistics.

Reviewed-by: Baolin Wang <baolin.w...@linux.alibaba.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
Acked-by: David Hildenbrand <da...@redhat.com>
Co-developed-by: Nico Pache <npa...@redhat.com>
Signed-off-by: Nico Pache <npa...@redhat.com>
Signed-off-by: Dev Jain <dev.j...@arm.com>
---

Cool! LGTM.

Reviewed-by: Lance Yang <lance.y...@linux.dev>

  Documentation/admin-guide/mm/transhuge.rst |  8 ++++++++
  include/linux/huge_mm.h                    |  2 ++
  mm/huge_memory.c                           |  4 ++++
  mm/khugepaged.c                            | 17 +++++++++++------
  4 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/mm/transhuge.rst 
b/Documentation/admin-guide/mm/transhuge.rst
index 1654211cc6cf..13269a0074d4 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -634,6 +634,14 @@ anon_fault_fallback_charge
        instead falls back to using huge pages with lower orders or
        small pages even though the allocation was successful.

+collapse_alloc

+       is incremented every time a huge page is successfully allocated for a
+       khugepaged collapse.
+
+collapse_alloc_failed
+       is incremented every time a huge page allocation fails during a
+       khugepaged collapse.
+
  zswpout
        is incremented every time a huge page is swapped out to zswap in one
        piece without splitting.
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 7698b3542c4f..3d29624c4f3f 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -128,6 +128,8 @@ enum mthp_stat_item {
        MTHP_STAT_ANON_FAULT_ALLOC,
        MTHP_STAT_ANON_FAULT_FALLBACK,
        MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
+       MTHP_STAT_COLLAPSE_ALLOC,
+       MTHP_STAT_COLLAPSE_ALLOC_FAILED,
        MTHP_STAT_ZSWPOUT,
        MTHP_STAT_SWPIN,
        MTHP_STAT_SWPIN_FALLBACK,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 370ecfd6a182..0063d1ba926e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -620,6 +620,8 @@ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
  DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, 
MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
+DEFINE_MTHP_STAT_ATTR(collapse_alloc, MTHP_STAT_COLLAPSE_ALLOC);
+DEFINE_MTHP_STAT_ATTR(collapse_alloc_failed, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
  DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
  DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
  DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
@@ -685,6 +687,8 @@ static struct attribute *any_stats_attrs[] = {
  #endif
        &split_attr.attr,
        &split_failed_attr.attr,
+       &collapse_alloc_attr.attr,
+       &collapse_alloc_failed_attr.attr,
        NULL,
  };

diff --git a/mm/khugepaged.c b/mm/khugepaged.c

index 6cf8700823f9..36ee659acfbb 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1061,21 +1061,26 @@ static int __collapse_huge_page_swapin(struct mm_struct 
*mm,
  }

static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,

-                             struct collapse_control *cc)
+               struct collapse_control *cc, unsigned int order)
  {
        gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
                     GFP_TRANSHUGE);
        int node = collapse_find_target_node(cc);
        struct folio *folio;

- folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, &cc->alloc_nmask);

+       folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
        if (!folio) {
                *foliop = NULL;
-               count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
+               if (order == HPAGE_PMD_ORDER)
+                       count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
+               count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED);
                return SCAN_ALLOC_HUGE_PAGE_FAIL;
        }

- count_vm_event(THP_COLLAPSE_ALLOC);

+       if (order == HPAGE_PMD_ORDER)
+               count_vm_event(THP_COLLAPSE_ALLOC);
+       count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC);
+
        if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
                folio_put(folio);
                *foliop = NULL;
@@ -1112,7 +1117,7 @@ static int collapse_huge_page(struct mm_struct *mm, 
unsigned long address,
         */
        mmap_read_unlock(mm);

- result = alloc_charge_folio(&folio, mm, cc);

+       result = alloc_charge_folio(&folio, mm, cc, HPAGE_PMD_ORDER);
        if (result != SCAN_SUCCEED)
                goto out_nolock;

@@ -1850,7 +1855,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,

        VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
        VM_BUG_ON(start & (HPAGE_PMD_NR - 1));

- result = alloc_charge_folio(&new_folio, mm, cc);

+       result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER);
        if (result != SCAN_SUCCEED)
                goto out;