From 821ed6bbed3cf41c4050a431eeb822b33868d36a Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan.kim@gmail.com>
Date: Tue, 24 May 2011 17:12:31 -0700
Subject: [PATCH] mm: filter unevictable page out in deactivate_page()

It's pointless that deactive_page's operates on unevictable pages.  This
patch removes unnecessary overhead which might be a bit problem in case
that there are many unevictable page in system(ex, mprotect workload)

[akpm@linux-foundation.org: tidy up comment]
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Rik van Riel<riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/swap.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/swap.c b/mm/swap.c
index 5602f1a1b1e7..2f365d1a4bb2 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -476,6 +476,13 @@ static void drain_cpu_pagevecs(int cpu)
  */
 void deactivate_page(struct page *page)
 {
+	/*
+	 * In a workload with many unevictable page such as mprotect, unevictable
+	 * page deactivation for accelerating reclaim is pointless.
+	 */
+	if (PageUnevictable(page))
+		return;
+
 	if (likely(get_page_unless_zero(page))) {
 		struct pagevec *pvec = &get_cpu_var(lru_deactivate_pvecs);