mm: memcontrol: convert NR_FILE_THPS account to pages

Currently we use struct per_cpu_nodestat to cache the vmstat counters,
which leads to inaccurate statistics especially THP vmstat counters.  In
the systems with if hundreds of processors it can be GBs of memory.  For
example, for a 96 CPUs system, the threshold is the maximum number of 125.
And the per cpu counters can cache 23.4375 GB in total.

The THP page is already a form of batched addition (it will add 512 worth
of memory in one go) so skipping the batching seems like sensible.
Although every THP stats update overflows the per-cpu counter, resorting
to atomic global updates.  But it can make the statistics more accuracy
for the THP vmstat counters.

So we convert the NR_FILE_THPS account to pages.  This patch is consistent
with 8f182270dfec ("mm/swap.c: flush lru pvecs on compound page arrival").
Doing this also can make the unit of vmstat counters more unified.
Finally, the unit of the vmstat counters are pages, kB and bytes.  The
B/KB suffix can tell us that the unit is bytes or kB.  The rest which is
without suffix are pages.

Link: https://lkml.kernel.org/r/20201228164110.2838-4-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Cc: Rafael. J. Wysocki <rafael@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

7 files changed, 14 insertions, 10 deletions

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 6da0c3508bc9..d5952f754911 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -466,8 +466,7 @@ static ssize_t node_read_meminfo(struct device *dev,
 				    HPAGE_PMD_NR),
 			     nid, K(node_page_state(pgdat, NR_SHMEM_PMDMAPPED) *
 				    HPAGE_PMD_NR),
-			     nid, K(node_page_state(pgdat, NR_FILE_THPS) *
-				    HPAGE_PMD_NR),
+			     nid, K(node_page_state(pgdat, NR_FILE_THPS)),
 			     nid, K(node_page_state(pgdat, NR_FILE_PMDMAPPED) *
 				    HPAGE_PMD_NR)
 #endif
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index a635c8a84ddf..7ea4679880c8 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -135,7 +135,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "ShmemPmdMapped: ",
 		    global_node_page_state(NR_SHMEM_PMDMAPPED) * HPAGE_PMD_NR);
 	show_val_kb(m, "FileHugePages:  ",
-		    global_node_page_state(NR_FILE_THPS) * HPAGE_PMD_NR);
+		    global_node_page_state(NR_FILE_THPS));
 	show_val_kb(m, "FilePmdMapped:  ",
 		    global_node_page_state(NR_FILE_PMDMAPPED) * HPAGE_PMD_NR);
 #endif
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 67d50ef5dd20..b751a9898bb6 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -219,7 +219,8 @@ static __always_inline bool vmstat_item_print_in_thp(enum node_stat_item item)
 	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
 		return false;
 
-	return item == NR_ANON_THPS;
+	return item == NR_ANON_THPS ||
+	       item == NR_FILE_THPS;
 }
 
 /*
diff --git a/mm/filemap.c b/mm/filemap.c
index 820d81901eae..9efe059e2b58 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -208,7 +208,7 @@ static void unaccount_page_cache_page(struct address_space *mapping,
 		if (PageTransHuge(page))
 			__dec_lruvec_page_state(page, NR_SHMEM_THPS);
 	} else if (PageTransHuge(page)) {
-		__dec_lruvec_page_state(page, NR_FILE_THPS);
+		__mod_lruvec_page_state(page, NR_FILE_THPS, -nr);
 		filemap_nr_thps_dec(mapping);
 	}
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 3691e863070a..77181faa2340 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2752,10 +2752,13 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
 		}
 		spin_unlock(&ds_queue->split_queue_lock);
 		if (mapping) {
+			int nr = thp_nr_pages(head);
+
 			if (PageSwapBacked(head))
 				__dec_lruvec_page_state(head, NR_SHMEM_THPS);
 			else
-				__dec_lruvec_page_state(head, NR_FILE_THPS);
+				__mod_lruvec_page_state(head, NR_FILE_THPS,
+							-nr);
 		}
 
 		__split_huge_page(page, list, end);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index fb0fdaec34d5..c427fe2ca7ff 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1643,6 +1643,7 @@ static void collapse_file(struct mm_struct *mm,
 	XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
 	int nr_none = 0, result = SCAN_SUCCEED;
 	bool is_shmem = shmem_file(file);
+	int nr;
 
 	VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
 	VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
@@ -1854,11 +1855,12 @@ out_unlock:
 		put_page(page);
 		goto xa_unlocked;
 	}
+	nr = thp_nr_pages(new_page);
 
 	if (is_shmem)
 		__inc_lruvec_page_state(new_page, NR_SHMEM_THPS);
 	else {
-		__inc_lruvec_page_state(new_page, NR_FILE_THPS);
+		__mod_lruvec_page_state(new_page, NR_FILE_THPS, nr);
 		filemap_nr_thps_inc(mapping);
 	}
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b2405f049006..fc552f57d3fb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1534,7 +1534,7 @@ static struct memory_stat memory_stats[] = {
 	 * constant(e.g. powerpc).
 	 */
 	{ "anon_thp", PAGE_SIZE, NR_ANON_THPS },
-	{ "file_thp", 0, NR_FILE_THPS },
+	{ "file_thp", PAGE_SIZE, NR_FILE_THPS },
 	{ "shmem_thp", 0, NR_SHMEM_THPS },
 #endif
 	{ "inactive_anon", PAGE_SIZE, NR_INACTIVE_ANON },
@@ -1566,8 +1566,7 @@ static int __init memory_stats_init(void)
 
 	for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-		if (memory_stats[i].idx == NR_FILE_THPS ||
-		    memory_stats[i].idx == NR_SHMEM_THPS)
+		if (memory_stats[i].idx == NR_SHMEM_THPS)
 			memory_stats[i].ratio = HPAGE_PMD_SIZE;
 #endif
 		VM_BUG_ON(!memory_stats[i].ratio);