[PATCH] mm: memcontrol: separate {pgscan,pgsteal}_{kswapd,direct} items in memory.stat of cgroup v2

[Qi Zheng <zhengqi.arch@bytedance.com>]

There are already statistics of {pgscan,pgsteal}_kswapd and
{pgscan,pgsteal}_direct of memcg event here, but now the sum
of the two is displayed in memory.stat of cgroup v2.

In order to obtain more accurate information during monitoring
and debugging, and to align with the display in /proc/vmstat,
it better to display {pgscan,pgsteal}_kswapd and
{pgscan,pgsteal}_direct separately.

Moreover, after this modification, all memcg events can be
printed with a combination of vm_event_name() and memcg_events().
This allows us to create an array to traverse and print, which
reduces redundant seq_buf_printf() codes.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 14 ++++--
 mm/memcontrol.c                         | 61 +++++++++++--------------
 2 files changed, 36 insertions(+), 39 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 176298f2f4de..0b9ca7e7df34 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1442,11 +1442,17 @@ PAGE_SIZE multiple when read back.
 	  pgrefill (npn)
 		Amount of scanned pages (in an active LRU list)
 
-	  pgscan (npn)
-		Amount of scanned pages (in an inactive LRU list)
+	  pgscan_kswapd (npn)
+		Amount of scanned pages by kswapd (in an inactive LRU list)
 
-	  pgsteal (npn)
-		Amount of reclaimed pages
+	  pgscan_direct (npn)
+		Amount of scanned pages directly  (in an inactive LRU list)
+
+	  pgsteal_kswapd (npn)
+		Amount of reclaimed pages by kswapd
+
+	  pgsteal_direct (npn)
+		Amount of reclaimed pages directly
 
 	  pgactivate (npn)
 		Amount of pages moved to the active LRU list
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0d3fe0a0c75a..4093062c5c9b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1460,6 +1460,28 @@ static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
 	return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
 }
 
+static const unsigned int memcg_vm_event_stat[] = {
+	PGFAULT,
+	PGMAJFAULT,
+	PGREFILL,
+	PGSCAN_KSWAPD,
+	PGSCAN_DIRECT,
+	PGSTEAL_KSWAPD,
+	PGSTEAL_DIRECT,
+	PGACTIVATE,
+	PGDEACTIVATE,
+	PGLAZYFREE,
+	PGLAZYFREED,
+#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
+	ZSWPIN,
+	ZSWPOUT,
+#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	THP_FAULT_ALLOC,
+	THP_COLLAPSE_ALLOC,
+#endif
+};
+
 static char *memory_stat_format(struct mem_cgroup *memcg)
 {
 	struct seq_buf s;
@@ -1495,41 +1517,10 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
 	}
 
 	/* Accumulated memory events */
-
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGFAULT),
-		       memcg_events(memcg, PGFAULT));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGMAJFAULT),
-		       memcg_events(memcg, PGMAJFAULT));
-	seq_buf_printf(&s, "%s %lu\n",  vm_event_name(PGREFILL),
-		       memcg_events(memcg, PGREFILL));
-	seq_buf_printf(&s, "pgscan %lu\n",
-		       memcg_events(memcg, PGSCAN_KSWAPD) +
-		       memcg_events(memcg, PGSCAN_DIRECT));
-	seq_buf_printf(&s, "pgsteal %lu\n",
-		       memcg_events(memcg, PGSTEAL_KSWAPD) +
-		       memcg_events(memcg, PGSTEAL_DIRECT));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGACTIVATE),
-		       memcg_events(memcg, PGACTIVATE));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGDEACTIVATE),
-		       memcg_events(memcg, PGDEACTIVATE));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREE),
-		       memcg_events(memcg, PGLAZYFREE));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(PGLAZYFREED),
-		       memcg_events(memcg, PGLAZYFREED));
-
-#if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(ZSWPIN),
-		       memcg_events(memcg, ZSWPIN));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(ZSWPOUT),
-		       memcg_events(memcg, ZSWPOUT));
-#endif
-
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_FAULT_ALLOC),
-		       memcg_events(memcg, THP_FAULT_ALLOC));
-	seq_buf_printf(&s, "%s %lu\n", vm_event_name(THP_COLLAPSE_ALLOC),
-		       memcg_events(memcg, THP_COLLAPSE_ALLOC));
-#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+	for (i = 0; i < ARRAY_SIZE(memcg_vm_event_stat); i++)
+		seq_buf_printf(&s, "%s %lu\n",
+			       vm_event_name(memcg_vm_event_stat[i]),
+			       memcg_events(memcg, memcg_vm_event_stat[i]));
 
 	/* The above should easily fit into one page */
 	WARN_ON_ONCE(seq_buf_has_overflowed(&s));
-- 
2.20.1