1 files changed, 25 insertions, 19 deletions

diff --git a/mm/workingset.c b/mm/workingset.c
index ef556bf1323d..241fa5d6b3b2 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -369,40 +369,46 @@ static unsigned long count_shadow_nodes(struct shrinker *shrinker,
 {
 	unsigned long max_nodes;
 	unsigned long nodes;
-	unsigned long pages;
+	unsigned long cache;
 
 	/* list_lru lock nests inside IRQ-safe mapping->tree_lock */
 	local_irq_disable();
 	nodes = list_lru_shrink_count(&shadow_nodes, sc);
 	local_irq_enable();
 
-	if (sc->memcg) {
-		pages = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
-						     LRU_ALL_FILE);
-	} else {
-		pages = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
-			node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
-	}
-
 	/*
-	 * Active cache pages are limited to 50% of memory, and shadow
-	 * entries that represent a refault distance bigger than that
-	 * do not have any effect.  Limit the number of shadow nodes
-	 * such that shadow entries do not exceed the number of active
-	 * cache pages, assuming a worst-case node population density
-	 * of 1/8th on average.
+	 * Approximate a reasonable limit for the radix tree nodes
+	 * containing shadow entries. We don't need to keep more
+	 * shadow entries than possible pages on the active list,
+	 * since refault distances bigger than that are dismissed.
+	 *
+	 * The size of the active list converges toward 100% of
+	 * overall page cache as memory grows, with only a tiny
+	 * inactive list. Assume the total cache size for that.
+	 *
+	 * Nodes might be sparsely populated, with only one shadow
+	 * entry in the extreme case. Obviously, we cannot keep one
+	 * node for every eligible shadow entry, so compromise on a
+	 * worst-case density of 1/8th. Below that, not all eligible
+	 * refaults can be detected anymore.
 	 *
 	 * On 64-bit with 7 radix_tree_nodes per page and 64 slots
 	 * each, this will reclaim shadow entries when they consume
-	 * ~2% of available memory:
+	 * ~1.8% of available memory:
 	 *
-	 * PAGE_SIZE / radix_tree_nodes / node_entries / PAGE_SIZE
+	 * PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
 	 */
-	max_nodes = pages >> (1 + RADIX_TREE_MAP_SHIFT - 3);
+	if (sc->memcg) {
+		cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
+						     LRU_ALL_FILE);
+	} else {
+		cache = node_page_state(NODE_DATA(sc->nid), NR_ACTIVE_FILE) +
+			node_page_state(NODE_DATA(sc->nid), NR_INACTIVE_FILE);
+	}
+	max_nodes = cache >> (RADIX_TREE_MAP_SHIFT - 3);
 
 	if (nodes <= max_nodes)
 		return 0;
-
 	return nodes - max_nodes;
 }