linux-kernel - [PATCH] mm/workingset.c: avoid unnecessary max_nodes estimation in count_shadow

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Message-ID: <20210123073825.46709-1-linmiaohe@huawei.com>
Date:   Sat, 23 Jan 2021 02:38:25 -0500
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] 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.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.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