[PATCH] mm/workingset.c: avoid unnecessary max_nodes estimation in count_shadow_nodes()

[Miaohe Lin]

If list_lru_shrink_count is 0, we always return SHRINK_EMPTY regardless of
the value of max_nodes. So we can return early if nodes == 0 to save some
cpu cycles of approximating a reasonable limit for the nodes.

Signed-off-by: Miaohe Lin <linmia...@huawei.com>
---
 mm/workingset.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 10e96de945b3..7db8f3dad13c 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -461,6 +461,8 @@ static unsigned long count_shadow_nodes(struct shrinker 
*shrinker,
        unsigned long pages;
 
        nodes = list_lru_shrink_count(&shadow_nodes, sc);
+       if (!nodes)
+               return SHRINK_EMPTY;
 
        /*
         * Approximate a reasonable limit for the nodes
@@ -503,9 +505,6 @@ static unsigned long count_shadow_nodes(struct shrinker 
*shrinker,
 
        max_nodes = pages >> (XA_CHUNK_SHIFT - 3);
 
-       if (!nodes)
-               return SHRINK_EMPTY;
-
        if (nodes <= max_nodes)
                return 0;
        return nodes - max_nodes;
-- 
2.19.1