From: Heesub Shin <heesub.shin@samsung.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Mel Gorman <mgorman@suse.de>, Heesub Shin <heesub.shin@samsung.com>,
        Dongjun Shin <d.j.shin@samsung.com>,
        Sunghwan Yun <sunghwan.yun@samsung.com>
Subject: [PATCH 2/2] mm/compaction: fix to initialize free scanner properly
Date: Thu, 03 Apr 2014 17:57:04 +0900
Message-id: <1396515424-18794-2-git-send-email-heesub.shin@samsung.com>
In-reply-to: <1396515424-18794-1-git-send-email-heesub.shin@samsung.com>
References: <1396515424-18794-1-git-send-email-heesub.shin@samsung.com>
DLP-Filter: Pass
Sender: linux-kernel-owner@vger.kernel.org

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@samsung.com>
Cc: Dongjun Shin <d.j.shin@samsung.com>
Cc: Sunghwan Yun <sunghwan.yun@samsung.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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