linux-kernel - [PATCH 44 of 66] skip transhuge pages in ksm for now

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Date:	Wed, 03 Nov 2010 16:28:19 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Cc:	Marcelo Tosatti <mtosatti@...hat.com>, Adam Litke <agl@...ibm.com>,
	Avi Kivity <avi@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mel@....ul.ie>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Chris Wright <chrisw@...s-sol.org>, bpicco@...hat.com,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Chris Mason <chris.mason@...cle.com>,
	Borislav Petkov <bp@...en8.de>
Subject: [PATCH 44 of 66] skip transhuge pages in ksm for now

From: Andrea Arcangeli <aarcange@...hat.com>

Skip transhuge pages in ksm for now.

Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
Reviewed-by: Rik van Riel <riel@...hat.com>
---

diff --git a/mm/ksm.c b/mm/ksm.c
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -430,7 +430,7 @@ static struct page *get_mergeable_page(s
 	page = follow_page(vma, addr, FOLL_GET);
 	if (IS_ERR_OR_NULL(page))
 		goto out;
-	if (PageAnon(page)) {
+	if (PageAnon(page) && !PageTransCompound(page)) {
 		flush_anon_page(vma, page, addr);
 		flush_dcache_page(page);
 	} else {
@@ -1288,7 +1288,19 @@ next_mm:
 			if (ksm_test_exit(mm))
 				break;
 			*page = follow_page(vma, ksm_scan.address, FOLL_GET);
-			if (!IS_ERR_OR_NULL(*page) && PageAnon(*page)) {
+			if (IS_ERR_OR_NULL(*page)) {
+				ksm_scan.address += PAGE_SIZE;
+				cond_resched();
+				continue;
+			}
+			if (PageTransCompound(*page)) {
+				put_page(*page);
+				ksm_scan.address &= HPAGE_PMD_MASK;
+				ksm_scan.address += HPAGE_PMD_SIZE;
+				cond_resched();
+				continue;
+			}
+			if (PageAnon(*page)) {
 				flush_anon_page(vma, *page, ksm_scan.address);
 				flush_dcache_page(*page);
 				rmap_item = get_next_rmap_item(slot,
@@ -1302,8 +1314,7 @@ next_mm:
 				up_read(&mm->mmap_sem);
 				return rmap_item;
 			}
-			if (!IS_ERR_OR_NULL(*page))
-				put_page(*page);
+			put_page(*page);
 			ksm_scan.address += PAGE_SIZE;
 			cond_resched();
 		}
--
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