linux-kernel - [RFC 2/3] mm: remain migratetype in freed page

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Date:	Tue, 17 Jul 2012 16:01:44 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan@...nel.org>
Subject: [RFC 2/3] mm: remain migratetype in freed page

Page allocator doesn't keep migratetype information to page
when the page is freed. This patch remains the information
to freed page's index field which isn't used by free/alloc
preparing so it shouldn't change any behavir except below one.

This patch adds a new call site in __free_pages_ok so it might be
overhead a bit but it's for high order allocation.
So I believe damage isn't hurt.

Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 include/linux/mm.h |    6 ++++--
 mm/page_alloc.c    |    7 ++++---
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 86d61d6..8fd32da 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -251,12 +251,14 @@ struct inode;
 
 static inline void set_page_migratetype(struct page *page, int migratetype)
 {
-	set_page_private(page, migratetype);
+	VM_BUG_ON((unsigned int)migratetype >= MIGRATE_TYPES);
+	page->index = migratetype;
 }
 
 static inline int get_page_migratetype(struct page *page)
 {
-	return page_private(page);
+	VM_BUG_ON((unsigned int)page->index >= MIGRATE_TYPES);
+	return page->index;
 }
 
 /*
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 103ba66..32985dd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -723,6 +723,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 {
 	unsigned long flags;
 	int wasMlocked = __TestClearPageMlocked(page);
+	int migratetype;
 
 	if (!free_pages_prepare(page, order))
 		return;
@@ -731,9 +732,9 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	if (unlikely(wasMlocked))
 		free_page_mlock(page);
 	__count_vm_events(PGFREE, 1 << order);
-	free_one_page(page_zone(page), page, order,
-					get_pageblock_migratetype(page));
-
+	migratetype = get_pageblock_migratetype(page);
+	set_page_migratetype(page, migratetype);
+	free_one_page(page_zone(page), page, order, migratetype);
 	local_irq_restore(flags);
 }
 
-- 
1.7.9.5

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