mm: add per-order mTHP anon_swpout and anon_swpout_fallback counters

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.

Link: https://lkml.kernel.org/r/20240412114858.407208-3-21cnbao@gmail.comSigned-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/huge_mm.h

@@ -268,6 +268,8 @@ enum mthp_stat_item {
 	MTHP_STAT_ANON_FAULT_ALLOC,
 	MTHP_STAT_ANON_FAULT_FALLBACK,
 	MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
+	MTHP_STAT_ANON_SWPOUT,
+	MTHP_STAT_ANON_SWPOUT_FALLBACK,
 	__MTHP_STAT_COUNT
 };
 

mm/huge_memory.c

@@ -555,11 +555,15 @@ 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(anon_swpout, MTHP_STAT_ANON_SWPOUT);
+DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
 
 static struct attribute *stats_attrs[] = {
 	&anon_fault_alloc_attr.attr,
 	&anon_fault_fallback_attr.attr,
 	&anon_fault_fallback_charge_attr.attr,
+	&anon_swpout_attr.attr,
+	&anon_swpout_fallback_attr.attr,
 	NULL,
 };
 

mm/page_io.c

@@ -217,6 +217,7 @@ static inline void count_swpout_vm_event(struct folio *folio)
 		count_memcg_folio_events(folio, THP_SWPOUT, 1);
 		count_vm_event(THP_SWPOUT);
 	}
+	count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_SWPOUT);
 #endif
 	count_vm_events(PSWPOUT, folio_nr_pages(folio));
 }

mm/vmscan.c

@@ -1214,6 +1214,8 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 						goto activate_locked;
 				}
 				if (!add_to_swap(folio)) {
+					int __maybe_unused order = folio_order(folio);
+
 					if (!folio_test_large(folio))
 						goto activate_locked_split;
 					/* Fallback to swap normal pages */
@@ -1225,6 +1227,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 							THP_SWPOUT_FALLBACK, 1);
 						count_vm_event(THP_SWPOUT_FALLBACK);
 					}
+					count_mthp_stat(order, MTHP_STAT_ANON_SWPOUT_FALLBACK);
 #endif
 					if (!add_to_swap(folio))
 						goto activate_locked_split;