[PATCH][mmotm] don't attempt to reclaim anon page in lumpy reclaimwhen no swap space is available

[Minchan Kim]

This patch is based on mmotm 2009-07-02-19-57 reverted 
'vmscan: don't attempt to reclaim anon page in lumpy reclaim when no swap space is available.'

This verssion is better than old one.
That's because enough swap space check is done in case of only lumpy reclaim. 
so it can't degrade performance in normal case.

== CUT HERE ==

VM already avoids attempting to reclaim anon pages in various places, But
it doesn't avoid it for lumpy reclaim.

It shuffles lru list unnecessary so that it is pointless.

Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
 mm/vmscan.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 27558aa..977af15 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -930,6 +930,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
 			/* Check that we have not crossed a zone boundary. */
 			if (unlikely(page_zone_id(cursor_page) != zone_id))
 				continue;
+			/*
+			 * If we don't have enough swap space, reclaiming of anon page
+			 * which don't already have a swap slot is pointless.
+			 */
+			if (nr_swap_pages <= 0 && (PageAnon(cursor_page) &&
+						!PageSwapCache(cursor_page)))
+				continue;
 			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
 				list_move(&cursor_page->lru, dst);
 				mem_cgroup_del_lru(cursor_page);
-- 
1.5.4.3



-- 
Kind regards,
Minchan Kim 
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