[PATCH] zoned vm counters: zone_reclaim: remove /proc/sys/vm/zone_reclaim_interval

The zone_reclaim_interval was necessary because we were not able to determine
how many unmapped pages exist in a zone.  Therefore we had to scan in
intervals to figure out if any pages were unmapped.

With the zoned counters and NR_ANON_PAGES we now know the number of pagecache
pages and the number of mapped pages in a zone.  So we can simply skip the
reclaim if there is an insufficient number of unmapped pages.  We use
SWAP_CLUSTER_MAX as the boundary.

Drop all support for /proc/sys/vm/zone_reclaim_interval.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 21 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2f0390161c0e..0960846d649f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1518,11 +1518,6 @@ int zone_reclaim_mode __read_mostly;
 #define RECLAIM_SLAB (1<<3)     /* Do a global slab shrink if the zone is out of memory */
 
 /*
- * Mininum time between zone reclaim scans
- */
-int zone_reclaim_interval __read_mostly = 30*HZ;
-
-/*
  * Priority for ZONE_RECLAIM. This determines the fraction of pages
  * of a node considered for each zone_reclaim. 4 scans 1/16th of
  * a zone.
@@ -1587,16 +1582,6 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 
         p->reclaim_state = NULL;
         current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
-
-        if (nr_reclaimed == 0) {
-                /*
-                 * We were unable to reclaim enough pages to stay on node.  We
-                 * now allow off node accesses for a certain time period before
-                 * trying again to reclaim pages from the local zone.
-                 */
-                zone->last_unsuccessful_zone_reclaim = jiffies;
-        }
-
         return nr_reclaimed >= nr_pages;
 }
 
@@ -1606,13 +1591,17 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         int node_id;
 
         /*
-         * Do not reclaim if there was a recent unsuccessful attempt at zone
-         * reclaim.  In that case we let allocations go off node for the
-         * zone_reclaim_interval.  Otherwise we would scan for each off-node
-         * page allocation.
+         * Do not reclaim if there are not enough reclaimable pages in this
+         * zone that would satify this allocations.
+         *
+         * All unmapped pagecache pages are reclaimable.
+         *
+         * Both counters may be temporarily off a bit so we use
+         * SWAP_CLUSTER_MAX as the boundary. It may also be good to
+         * leave a few frequently used unmapped pagecache pages around.
          */
-        if (time_before(jiffies,
-                zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
+        if (zone_page_state(zone, NR_FILE_PAGES) -
+                zone_page_state(zone, NR_FILE_MAPPED) < SWAP_CLUSTER_MAX)
                         return 0;
 
         /*