vmscan: evict use-once pages first

[mirror_ubuntu-artful-kernel.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e5245d051647e6271604c613f9ebc8685e2884e7..9673437a54572790fcc77da4ab2b9aa8b67a5582 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1351,12 +1351,48 @@ static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc)
        return low;
 }
 
+static int inactive_file_is_low_global(struct zone *zone)
+{
+       unsigned long active, inactive;
+
+       active = zone_page_state(zone, NR_ACTIVE_FILE);
+       inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+
+       return (active > inactive);
+}
+
+/**
+ * inactive_file_is_low - check if file pages need to be deactivated
+ * @zone: zone to check
+ * @sc:   scan control of this context
+ *
+ * When the system is doing streaming IO, memory pressure here
+ * ensures that active file pages get deactivated, until more
+ * than half of the file pages are on the inactive list.
+ *
+ * Once we get to that situation, protect the system's working
+ * set from being evicted by disabling active file page aging.
+ *
+ * This uses a different ratio than the anonymous pages, because
+ * the page cache uses a use-once replacement algorithm.
+ */
+static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
+{
+       int low;
+
+       if (scanning_global_lru(sc))
+               low = inactive_file_is_low_global(zone);
+       else
+               low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup);
+       return low;
+}
+
 static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
        struct zone *zone, struct scan_control *sc, int priority)
 {
        int file = is_file_lru(lru);
 
-       if (lru == LRU_ACTIVE_FILE) {
+       if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
                shrink_active_list(nr_to_scan, zone, sc, priority, file);
                return 0;
        }