memcg: fix event counting breakage from recent THP update

Changes in e401f1761 ("memcg: modify accounting function for supporting
THP better") adds nr_pages to support multiple page size in
memory_cgroup_charge_statistics.

But counting the number of event nees abs(nr_pages) for increasing
counters.  This patch fixes event counting.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fc75f34ba609..da53a252b259 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -612,8 +612,10 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
         /* pagein of a big page is an event. So, ignore page size */
         if (nr_pages > 0)
                 __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGIN_COUNT]);
-        else
+        else {
                 __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGOUT_COUNT]);
+                nr_pages = -nr_pages; /* for event */
+        }
 
         __this_cpu_add(mem->stat->count[MEM_CGROUP_EVENTS], nr_pages);