mm: vmscan: kswapd should not free an excessive number of pages when balancing small...

[linux-flexiantxendom0-natty.git] / mm / vmscan.c

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a578535..f50f716 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2406,6 +2406,7 @@ loop_again:
                for (i = 0; i <= end_zone; i++) {
                        struct zone *zone = pgdat->node_zones + i;
                        int nr_slab;
+                       unsigned long balance_gap;
 
                        if (!populated_zone(zone))
                                continue;
@@ -2422,11 +2423,20 @@ loop_again:
                        mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);
 
                        /*
-                        * We put equal pressure on every zone, unless one
-                        * zone has way too many pages free already.
+                        * We put equal pressure on every zone, unless
+                        * one zone has way too many pages free
+                        * already. The "too many pages" is defined
+                        * as the high wmark plus a "gap" where the
+                        * gap is either the low watermark or 1%
+                        * of the zone, whichever is smaller.
                         */
+                       balance_gap = min(low_wmark_pages(zone),
+                               (zone->present_pages +
+                                       KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+                               KSWAPD_ZONE_BALANCE_GAP_RATIO);
                        if (!zone_watermark_ok_safe(zone, order,
-                                       8*high_wmark_pages(zone), end_zone, 0))
+                                       high_wmark_pages(zone) + balance_gap,
+                                       end_zone, 0))
                                shrink_zone(priority, zone, &sc);
                        reclaim_state->reclaimed_slab = 0;
                        nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,