[PATCH 7.2 v16 02/13] mm/khugepaged: generalize alloc_charge_folio()

Nico Pache
2026-04-19T18:59:20Z

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

Pass order to alloc_charge_folio() and update mTHP statistics.

Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Co-developed-by: Nico Pache <npache@redhat.com>
Signed-off-by: Nico Pache <npache@redhat.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
---
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 5fbc3d89bb07..c51932e6275d 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -639,6 +639,14 @@ 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 2949e5acff35..ba7ae6808544 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 970e077019b7..345c54133c83 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -685,6 +685,8 @@ 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);
@@ -750,6 +752,8 @@ 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 53e7e4be172d..afac6bc4e76d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1068,21 +1068,26 @@ static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,
}

static enum scan_result 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 (is_pmd_order(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 (is_pmd_order(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;
@@ -1118,7 +1123,7 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a
*/
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;

@@ -1899,7 +1904,7 @@ static enum scan_result 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;

--
2.53.0