[PATCH] zone_reclaim: configurable off node allocation period.

Currently the zone_reclaim code has a fixed window of 30 seconds of off node
allocations should a local zone have no unused pagecache pages left.  Reclaim
will be attempted again after this timeout period to avoid repeated useless
scans for memory.  This is also useful to established sufficiently large off
node allocation chunks to relieve the local node.

It may be beneficial to adjust that time period for some special situations.
For example if memory use was exceeding node capacity one may want to give up
for longer periods of time.  If memory spikes intermittendly then one may want
to shorten the time period to reduce the number of off node allocations.

This patch allows just that....

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, 2 insertions, 2 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f8b94ea6f722..8760a4abfa1f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1595,7 +1595,7 @@ int zone_reclaim_mode __read_mostly;
 /*
  * Mininum time between zone reclaim scans
  */
-#define ZONE_RECLAIM_INTERVAL 30*HZ
+int zone_reclaim_interval __read_mostly = 30*HZ;
 
 /*
  * Priority for ZONE_RECLAIM. This determines the fraction of pages
@@ -1617,7 +1617,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
         int node_id;
 
         if (time_before(jiffies,
-                zone->last_unsuccessful_zone_reclaim + ZONE_RECLAIM_INTERVAL))
+                zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval))
                         return 0;
 
         if (!(gfp_mask & __GFP_WAIT) ||