linux-kernel - [PATCH] Clear reference bit although page isn't mapped.

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Message-Id: <20091202115358.5C4F.A69D9226@jp.fujitsu.com>
Date:	Wed,  2 Dec 2009 11:55:27 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Larry Woodman <lwoodman@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: [PATCH] Clear reference bit although page isn't mapped.

> btw, current shrink_active_list() have unnecessary page_mapping_inuse() call.
> it prevent to drop page reference bit from unmapped cache page. it mean
> we protect unmapped cache page than mapped page. it is strange.

How about this?

---------------------------------
SplitLRU VM replacement algorithm assume shrink_active_list() clear
the page's reference bit. but unnecessary page_mapping_inuse() test
prevent it.

This patch remove it.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
---
 mm/vmscan.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 00156f2..3e942b5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1347,8 +1347,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
 		}
 
 		/* page_referenced clears PageReferenced */
-		if (page_mapping_inuse(page) &&
-		    page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
+		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
 			nr_rotated++;
 			/*
 			 * Identify referenced, file-backed active pages and
-- 
1.6.5.2



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