[PATCH] CMA: decrease cc.nr_migratepages after reclaiming pagelist

[PATCH] CMA: decrease cc.nr_migratepages after reclaiming pagelist

[Minchan Kim]

The reclaim_clean_pages_from_list reclaims clean pages before
migration so cc.nr_migratepages should be updated.
Currently, there is no problem but it can be wrong if we
try to use the vaule in future.

Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
I found this problem during I develop new feature. :(

 mm/page_alloc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 296bea9..4b7dced 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5669,7 +5669,7 @@ static unsigned long pfn_max_align_up(unsigned long pfn)
 static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
 {
 	/* This function is based on compact_zone() from compaction.c. */
-
+	unsigned long nr_reclaimed;
 	unsigned long pfn = start;
 	unsigned int tries = 0;
 	int ret = 0;
@@ -5705,7 +5705,9 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
 			break;
 		}
 
-		reclaim_clean_pages_from_list(cc.zone, &cc.migratepages);
+		nr_reclaimed = reclaim_clean_pages_from_list(cc.zone,
+							&cc.migratepages);
+		cc.nr_migratepages -= nr_reclaimed;
 
 		ret = migrate_pages(&cc.migratepages,
 				    alloc_migrate_target,
-- 
1.7.9.5

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Re: [PATCH] CMA: decrease cc.nr_migratepages after reclaiming pagelist

[Mel Gorman]

On Wed, Sep 26, 2012 at 03:50:12PM +0900, Minchan Kim wrote:
> The reclaim_clean_pages_from_list reclaims clean pages before
> migration so cc.nr_migratepages should be updated.
> Currently, there is no problem but it can be wrong if we
> try to use the vaule in future.
> 
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Minchan Kim <minchan@kernel.org>

Yeah ok. As you say, it shouldn't actually affect anything currently and
cc.migratepages is expected to go out of date after migration meaning we
need update_nr_listpages. This patch looks ok though.

Acked-by: Mel Gorman <mgorman@suse.de>

-- 
Mel Gorman
SUSE Labs

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