mm: memcg: keep ratelimit counter separate from event counters

All events except the ratelimit counter are statistics exported to
userspace.  Keep this internal value out of the event count array.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ying Han <yinghan@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -94,7 +94,6 @@ enum mem_cgroup_stat_index {
 enum mem_cgroup_events_index {
 	MEM_CGROUP_EVENTS_PGPGIN,	/* # of pages paged in */
 	MEM_CGROUP_EVENTS_PGPGOUT,	/* # of pages paged out */
-	MEM_CGROUP_EVENTS_COUNT,	/* # of pages paged in/out */
 	MEM_CGROUP_EVENTS_PGFAULT,	/* # of page-faults */
 	MEM_CGROUP_EVENTS_PGMAJFAULT,	/* # of major page-faults */
 	MEM_CGROUP_EVENTS_NSTATS,
@@ -118,6 +117,7 @@ enum mem_cgroup_events_target {
 struct mem_cgroup_stat_cpu {
 	long count[MEM_CGROUP_STAT_NSTATS];
 	unsigned long events[MEM_CGROUP_EVENTS_NSTATS];
+	unsigned long nr_page_events;
 	unsigned long targets[MEM_CGROUP_NTARGETS];
 };
 
@@ -716,7 +716,7 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
 		nr_pages = -nr_pages; /* for event */
 	}
 
-	__this_cpu_add(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT], nr_pages);
+	__this_cpu_add(memcg->stat->nr_page_events, nr_pages);
 
 	preempt_enable();
 }
@@ -777,7 +777,7 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
 {
 	unsigned long val, next;
 
-	val = __this_cpu_read(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT]);
+	val = __this_cpu_read(memcg->stat->nr_page_events);
 	next = __this_cpu_read(memcg->stat->targets[target]);
 	/* from time_after() in jiffies.h */
 	if ((long)next - (long)val < 0) {