[PATCH] mm: Do not deactivate when the cgroup has plenty inactive page

[zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>]

After appling the series patches(mm: fix page aging across multiple cgroups),
cgroup memory reclaim strategy is based on reclaim root's inactive:active
ratio. if the target lruvec need to deactivate, its children cgroup also will
deactivate. That will result in hot page to be reclaimed and other cgroup's
cold page will be left, which is not expected.

The patch will not force deactivate when inactive_is_low is not true unless
we has scanned the inactive list and memory is unable to reclaim.

Signed-off-by: zhongjiang-ali <zhongjiang-ali@linux.alibaba.com>
---
 mm/vmscan.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 466fc31..77d395f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2407,8 +2407,21 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
 		case SCAN_FILE:
 		case SCAN_ANON:
 			/* Scan one type exclusively */
-			if ((scan_balance == SCAN_FILE) != file)
+			if ((scan_balance == SCAN_FILE) != file) {
 				scan = 0;
+			} else {
+				/*
+				 * Reclaim memory is based on the root's inactive: active
+				 * ratio, but it is possible that silbing cgroup has a lot
+				 * of cold memory to reclaim rather than reclaim the hot
+				 * cache in the current cgroup.
+				 */
+				if (!sc->force_deactivate && is_active_lru(lru) &&
+						!inactive_is_low(lruvec, lru - LRU_ACTIVE)) {
+					if (sc->may_deactivate & (1 << file))
+						scan = 0;
+				}
+			}
 			break;
 		default:
 			/* Look ma, no brain */
-- 
1.8.3.1