1 files changed, 41 insertions, 0 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index cb8ad3c6e483..bbd194630c5b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -932,6 +932,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
                 long mapped_ratio;
                 long distress;
                 long swap_tendency;
+                long imbalance;
 
                 if (zone_is_near_oom(zone))
                         goto force_reclaim_mapped;
@@ -967,6 +968,46 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
                 swap_tendency = mapped_ratio / 2 + distress + sc->swappiness;
 
                 /*
+                 * If there's huge imbalance between active and inactive
+                 * (think active 100 times larger than inactive) we should
+                 * become more permissive, or the system will take too much
+                 * cpu before it start swapping during memory pressure.
+                 * Distress is about avoiding early-oom, this is about
+                 * making swappiness graceful despite setting it to low
+                 * values.
+                 *
+                 * Avoid div by zero with nr_inactive+1, and max resulting
+                 * value is vm_total_pages.
+                 */
+                imbalance  = zone_page_state(zone, NR_ACTIVE);
+                imbalance /= zone_page_state(zone, NR_INACTIVE) + 1;
+
+                /*
+                 * Reduce the effect of imbalance if swappiness is low,
+                 * this means for a swappiness very low, the imbalance
+                 * must be much higher than 100 for this logic to make
+                 * the difference.
+                 *
+                 * Max temporary value is vm_total_pages*100.
+                 */
+                imbalance *= (vm_swappiness + 1);
+                imbalance /= 100;
+
+                /*
+                 * If not much of the ram is mapped, makes the imbalance
+                 * less relevant, it's high priority we refill the inactive
+                 * list with mapped pages only in presence of high ratio of
+                 * mapped pages.
+                 *
+                 * Max temporary value is vm_total_pages*100.
+                 */
+                imbalance *= mapped_ratio;
+                imbalance /= 100;
+
+                /* apply imbalance feedback to swap_tendency */
+                swap_tendency += imbalance;
+
+                /*
                  * Now use this metric to decide whether to start moving mapped
                  * memory onto the inactive list.
                  */