2 files changed, 20 insertions, 0 deletions

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 4bca2a3d9174..a46c10fcddfc 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -137,6 +137,7 @@ This is value ORed together of
 1       = Zone reclaim on
 2       = Zone reclaim writes dirty pages out
 4       = Zone reclaim swaps pages
+8       = Also do a global slab reclaim pass
 
 zone_reclaim_mode is set during bootup to 1 if it is determined that pages
 from remote zones will cause a measurable performance reduction. The
@@ -160,6 +161,11 @@ Allowing regular swap effectively restricts allocations to the local
 node unless explicitly overridden by memory policies or cpuset
 configurations.
 
+It may be advisable to allow slab reclaim if the system makes heavy
+use of files and builds up large slab caches. However, the slab
+shrink operation is global, may take a long time and free slabs
+in all nodes of the system.
+
 ================================================================
 
 zone_reclaim_interval:
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9e2ef3624d77..aa4b80dbe3ad 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1596,6 +1596,7 @@ int zone_reclaim_mode __read_mostly;
 #define RECLAIM_ZONE (1<<0)     /* Run shrink_cache on the zone */
 #define RECLAIM_WRITE (1<<1)    /* Writeout pages during reclaim */
 #define RECLAIM_SWAP (1<<2)     /* Swap pages out during reclaim */
+#define RECLAIM_SLAB (1<<3)     /* Do a global slab shrink if the zone is out of memory */
 
 /*
  * Mininum time between zone reclaim scans
@@ -1666,6 +1667,19 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
 
         } while (sc.nr_reclaimed < nr_pages && sc.priority > 0);
 
+        if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) {
+                /*
+                 * shrink_slab does not currently allow us to determine
+                 * how many pages were freed in the zone. So we just
+                 * shake the slab and then go offnode for a single allocation.
+                 *
+                 * shrink_slab will free memory on all zones and may take
+                 * a long time.
+                 */
+                shrink_slab(sc.nr_scanned, gfp_mask, order);
+                sc.nr_reclaimed = 1;    /* Avoid getting the off node timeout */
+        }
+
         p->reclaim_state = NULL;
         current->flags &= ~PF_MEMALLOC;