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

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.

Link: https://lkml.kernel.org/r/20210123073825.46709-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/workingset.c b/mm/workingset.c
index 10e96de..7db8f3d 100644 (file)
--- 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;