linux-kernel - [PATCH] more mapcount page as kpage could reduce total replacement times than fewer mapcount one in probability.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 14 Jun 2016 17:17:37 +0800
From:	<zhouxianrong@...wei.com>
To:	<linux-mm@...ck.org>
CC:	<akpm@...ux-foundation.org>, <hughd@...gle.com>,
	<aarcange@...hat.com>, <kirill.shutemov@...ux.intel.com>,
	<dave.hansen@...ux.intel.com>, <zhouchengming1@...wei.com>,
	<geliangtang@....com>, <zhouxianrong@...wei.com>,
	<linux-kernel@...r.kernel.org>, <zhouxiyu@...wei.com>,
	<wanghaijun5@...wei.com>
Subject: [PATCH] more mapcount page as kpage could reduce total replacement times than fewer mapcount one in probability.

From: z00281421 <z00281421@...esmail.huawei.com>

more mapcount page as kpage could reduce total replacement 
times than fewer mapcount one when ksmd scan and replace 
among forked pages later.

Signed-off-by: z00281421 <z00281421@...esmail.huawei.com>
---
 mm/ksm.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/mm/ksm.c b/mm/ksm.c
index 4786b41..17a238c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1094,6 +1094,21 @@ static struct page *try_to_merge_two_pages(struct rmap_item *rmap_item,
 {
 	int err;
 
+	/*
+	 * select more mapcount page as kpage
+	 */
+	if (page_mapcount(page) < page_mapcount(tree_page)) {
+		struct page *tmp_page;
+		struct rmap_item *tmp_rmap_item;
+
+		tmp_page = page;
+		page = tree_page;
+		tree_page = tmp_page;
+		tmp_rmap_item = rmap_item;
+		rmap_item = tree_rmap_item;
+		tree_rmap_item = tmp_rmap_item;
+	}
+
 	err = try_to_merge_with_ksm_page(rmap_item, page, NULL);
 	if (!err) {
 		err = try_to_merge_with_ksm_page(tree_rmap_item,
-- 
1.7.9.5