[PATCH v2] mm/vmscan: get number of pages on the LRU list in memcgroup base on lru_zone_size

[Honglei Wang <honglei.wang@oracle.com>]

lruvec_lru_size() is involving lruvec_page_state_local() to get the
lru_size in the current code. It's base on lruvec_stat_local.count[]
of mem_cgroup_per_node. This counter is updated in batch. It won't
do charge if the number of coming pages doesn't meet the needs of
MEMCG_CHARGE_BATCH who's defined as 32 now.

The testcase in LTP madvise09[1] fails due to small block memory is
not charged. It creates a new memcgroup and sets up 32 MADV_FREE
pages. Then it forks child who will introduce memory pressure in the
memcgroup. The MADV_FREE pages are expected to be released under the
pressure, but 32 is not more than MEMCG_CHARGE_BATCH and these pages
won't be charged in lruvec_stat_local.count[] until some more pages
come in to satisfy the needs of batch charging. So these MADV_FREE
pages can't be freed in memory pressure which is a bit conflicted
with the definition of MADV_FREE.

Getting lru_size base on lru_zone_size of mem_cgroup_per_node which
is not updated in batch can make it a bit more accurate in similar
scenario.

[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/madvise/madvise09.c

Signed-off-by: Honglei Wang <honglei.wang@oracle.com>
---
 mm/vmscan.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c77d1e3761a7..c28672460868 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -354,12 +354,13 @@ unsigned long zone_reclaimable_pages(struct zone *zone)
  */
 unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx)
 {
-	unsigned long lru_size;
+	unsigned long lru_size = 0;
 	int zid;
 
-	if (!mem_cgroup_disabled())
-		lru_size = lruvec_page_state_local(lruvec, NR_LRU_BASE + lru);
-	else
+	if (!mem_cgroup_disabled()) {
+		for (zid = 0; zid < MAX_NR_ZONES; zid++)
+			lru_size += mem_cgroup_get_zone_lru_size(lruvec, lru, zid);
+	} else
 		lru_size = node_page_state(lruvec_pgdat(lruvec), NR_LRU_BASE + lru);
 
 	for (zid = zone_idx + 1; zid < MAX_NR_ZONES; zid++) {
-- 
2.17.0