[PATCH v4 2/2] mm: add per-order mTHP anon_swpout and anon_swpout_fallback counters

[Barry Song]

From: Barry Song <v-songbaohua@xxxxxxxx>

This helps to display the fragmentation situation of the swapfile,
knowing the proportion of how much we haven't split large folios.
So far, we only support non-split swapout for anon memory, with
the possibility of expanding to shmem in the future.  So, we add
the "anon" prefix to the counter names.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
 include/linux/huge_mm.h | 2 ++
 mm/huge_memory.c        | 4 ++++
 mm/page_io.c            | 6 +++++-
 mm/vmscan.c             | 3 +++
 4 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index c5d33017a4dd..1d893a358df6 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -267,6 +267,8 @@ unsigned long thp_vma_allowable_orders(struct vm_area_struct *vma,
 enum mthp_stat_item {
 	MTHP_STAT_ANON_ALLOC,
 	MTHP_STAT_ANON_ALLOC_FALLBACK,
+	MTHP_STAT_ANON_SWPOUT,
+	MTHP_STAT_ANON_SWPOUT_FALLBACK,
 	__MTHP_STAT_COUNT
 };
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5b875f0fc923..28113f8fdf18 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -554,10 +554,14 @@ static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
 
 DEFINE_MTHP_STAT_ATTR(anon_alloc, MTHP_STAT_ANON_ALLOC);
 DEFINE_MTHP_STAT_ATTR(anon_alloc_fallback, MTHP_STAT_ANON_ALLOC_FALLBACK);
+DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
+DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
 
 static struct attribute *stats_attrs[] = {
 	&anon_alloc_attr.attr,
 	&anon_alloc_fallback_attr.attr,
+	&anon_swpout_attr.attr,
+	&anon_swpout_fallback_attr.attr,
 	NULL,
 };
 
diff --git a/mm/page_io.c b/mm/page_io.c
index a9a7c236aecc..7669452e8b4d 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -212,13 +212,17 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
 
 static inline void count_swpout_vm_event(struct folio *folio)
 {
+	long nr_pages = folio_nr_pages(folio);
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (unlikely(folio_test_pmd_mappable(folio))) {
 		count_memcg_folio_events(folio, THP_SWPOUT, 1);
 		count_vm_event(THP_SWPOUT);
 	}
+	if (nr_pages > 0)
+		count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPOUT);
 #endif
-	count_vm_events(PSWPOUT, folio_nr_pages(folio));
+	count_vm_events(PSWPOUT, nr_pages);
 }
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ffc4553c8615..b30e6294f82a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1247,6 +1247,9 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 						count_vm_event(
 							THP_SWPOUT_FALLBACK);
 					}
+					if (nr_pages > 0)
+						count_mthp_stat(get_order(nr_pages * PAGE_SIZE),
+							MTHP_STAT_ANON_SWPOUT_FALLBACK);
 #endif
 					if (!add_to_swap(folio))
 						goto activate_locked_split;
-- 
2.34.1