[patch 1/1] vmscan: give referenced, active and unmapped pages a second trip around the LRU

[akpm@linux-foundation.org]

Martin spotted this.

In the original rmap conversion in 2.5.32 we broke aging of pagecache pages on
the active list: we deactivate these pages even if they had PG_referenced set.

We should instead clear PG_referenced and give these pages another trip around
the active list.

We have basically no way of working out whether or not this change will
benefit or worsen anything.

Cc: Martin Bligh <mbligh@mbligh.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    3 +++
 1 files changed, 3 insertions(+)

diff -puN mm/vmscan.c~vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru mm/vmscan.c
--- a/mm/vmscan.c~vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru
+++ a/mm/vmscan.c
@@ -836,6 +836,9 @@ force_reclaim_mapped:
 				list_add(&page->lru, &l_active);
 				continue;
 			}
+		} else if (TestClearPageReferenced(page)) {
+			list_add(&page->lru, &l_active);
+			continue;
 		}
 		list_add(&page->lru, &l_inactive);
 	}
_

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