[PATCH] zone reclaim with slab: avoid unecessary off node allocations

Minor performance fix.

If we reclaimed enough slab pages from a zone then we can avoid going off
node with the current allocation.  Take care of updating nr_reclaimed when
reclaiming from the slab.

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, 12 insertions, 5 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 089e943c4d38..b950f193816e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1566,6 +1566,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
                 .gfp_mask = gfp_mask,
                 .swappiness = vm_swappiness,
         };
+        unsigned long slab_reclaimable;
 
         disable_swap_token();
         cond_resched();
@@ -1592,7 +1593,8 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
                 } while (priority >= 0 && nr_reclaimed < nr_pages);
         }
 
-        if (zone_page_state(zone, NR_SLAB_RECLAIMABLE) > zone->min_slab_pages) {
+        slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
+        if (slab_reclaimable > zone->min_slab_pages) {
                 /*
                  * shrink_slab() does not currently allow us to determine how
                  * many pages were freed in this zone. So we take the current
@@ -1603,12 +1605,17 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
                  * Note that shrink_slab will free memory on all zones and may
                  * take a long time.
                  */
-                unsigned long limit = zone_page_state(zone,
-                                NR_SLAB_RECLAIMABLE) - nr_pages;
-
                 while (shrink_slab(sc.nr_scanned, gfp_mask, order) &&
-                        zone_page_state(zone, NR_SLAB_RECLAIMABLE) > limit)
+                        zone_page_state(zone, NR_SLAB_RECLAIMABLE) >
+                                slab_reclaimable - nr_pages)
                         ;
+
+                /*
+                 * Update nr_reclaimed by the number of slab pages we
+                 * reclaimed from this zone.
+                 */
+                nr_reclaimed += slab_reclaimable -
+                        zone_page_state(zone, NR_SLAB_RECLAIMABLE);
         }
 
         p->reclaim_state = NULL;