linux-kernel - [PATCH] mm: trivial mark_page

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Message-ID: <20191016225326.GB12497@wfg-t540p.sh.intel.com>
Date:   Thu, 17 Oct 2019 06:53:26 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Linux Memory Management List <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Wu Fengguang <fengguang.wu@...el.com>,
        Liu Jingqi <jingqi.liu@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm: trivial mark_page_accessed() cleanup

This avoids duplicated PageReferenced() calls.
No behavior change.

Signed-off-by: Fengguang Wu <fengguang.wu@...el.com>
---
  mm/swap.c | 14 +++++++++-----
  1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 38a52b9..c55720c 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -373,9 +373,15 @@ void mark_page_accessed(struct page *page)
  	page = compound_head(page);
  	inc_node_page_state(page, NR_ACCESSED);
  
-	if (!PageActive(page) && !PageUnevictable(page) &&
-			PageReferenced(page)) {
-
+	if (!PageReferenced(page)) {
+		SetPageReferenced(page);
+	} else if (PageUnevictable(page)) {
+		/*
+		 * Unevictable pages are on the "LRU_UNEVICTABLE" list. But,
+		 * this list is never rotated or maintained, so marking an
+		 * evictable page accessed has no effect.
+		 */
+	} else if (!PageActive(page)) {
  		/*
  		 * If the page is on the LRU, queue it for activation via
  		 * activate_page_pvecs. Otherwise, assume the page is on a
@@ -389,8 +395,6 @@ void mark_page_accessed(struct page *page)
  		ClearPageReferenced(page);
  		if (page_is_file_cache(page))
  			workingset_activation(page);
-	} else if (!PageReferenced(page)) {
-		SetPageReferenced(page);
  	}
  	if (page_is_idle(page))
  		clear_page_idle(page);
-- 
2.7.4