linux-kernel - [PATCH 2/2] mm/compaction: fix to initialize free scanner properly

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Date:	Thu, 03 Apr 2014 17:57:04 +0900
From:	Heesub Shin <heesub.shin@...sung.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>,
	Heesub Shin <heesub.shin@...sung.com>,
	Dongjun Shin <d.j.shin@...sung.com>,
	Sunghwan Yun <sunghwan.yun@...sung.com>
Subject: [PATCH 2/2] mm/compaction: fix to initialize free scanner properly

Free scanner does not works well on systems having zones which do not
span to pageblock-aligned boundary.

zone->compact_cached_free_pfn is reset when the migration and free
scanner across or compaction restarts. After the reset, if end_pfn of
the zone was not aligned to pageblock_nr_pages, free scanner tries to
isolate free pages from the middle of pageblock to the end, which can
be very small range.

Signed-off-by: Heesub Shin <heesub.shin@...sung.com>
Cc: Dongjun Shin <d.j.shin@...sung.com>
Cc: Sunghwan Yun <sunghwan.yun@...sung.com>
---
 mm/compaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 1ef9144..fefe1da 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -983,7 +983,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
 	 */
 	cc->migrate_pfn = zone->compact_cached_migrate_pfn;
 	cc->free_pfn = zone->compact_cached_free_pfn;
-	if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
+	if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) {
 		cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
 		zone->compact_cached_free_pfn = cc->free_pfn;
 	}
-- 
1.8.3.2

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