[PATCH -mm 09/16] fix pagecache reclaim referenced bit check

[Rik van Riel <riel@redhat.com>]

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From: Rik van Riel <riel@redhat.com>

The -mm tree contains the patch
vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
which gives referenced pagecache pages another trip around
the active list.  This seems to help keep frequently accessed
pagecache pages in memory.

However, it means that pagecache pages that get moved to the
inactive list do not have their referenced bit set, and a
reference to the page will not get it moved back to the active
list.  This patch sets the referenced bit on pagecache pages
that get deactivated, so the next access to the page will promote
it back to the active list.

---
 mm/vmscan.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6.26-rc2-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.26-rc2-mm1.orig/mm/vmscan.c	2008-05-23 14:21:35.000000000 -0400
+++ linux-2.6.26-rc2-mm1/mm/vmscan.c	2008-05-23 14:21:35.000000000 -0400
@@ -1060,6 +1060,10 @@ static void shrink_active_list(unsigned 
 			if (!file)
 				/* Anonymous pages always get deactivated. */
 				pgmoved++;
+			else if (!page_mapped(page))
+				/* Bypass use-once, make the next access count.
+				 * See mark_page_accessed. */
+				SetPageReferenced(page);
 		}
 	}
 

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