[PATCH 07/27] mm, vmscan: Remove balance gap

[Mel Gorman]

The balance gap was introduced to apply equal pressure to all zones when
reclaiming for a higher zone. With node-based LRU, the need for the balance
gap is removed and the code is dead so remove it.

Signed-off-by: Mel Gorman <mgor...@techsingularity.net>
---
 mm/vmscan.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9368af4cfb06..96bf841f9352 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2488,7 +2488,7 @@ static bool shrink_node(pg_data_t *pgdat, struct 
scan_control *sc,
  */
 static inline bool compaction_ready(struct zone *zone, int order, int 
classzone_idx)
 {
-       unsigned long balance_gap, watermark;
+       unsigned long watermark;
        bool watermark_ok;
 
        /*
@@ -2497,9 +2497,7 @@ static inline bool compaction_ready(struct zone *zone, 
int order, int classzone_
         * there is a buffer of free pages available to give compaction
         * a reasonable chance of completing and allocating the page
         */
-       balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP(
-                       zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO));
-       watermark = high_wmark_pages(zone) + balance_gap + (2UL << order);
+       watermark = high_wmark_pages(zone) + (2UL << order);
        watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 
classzone_idx);
 
        /*
@@ -2962,10 +2960,9 @@ static void age_active_anon(struct pglist_data *pgdat,
        } while (memcg);
 }
 
-static bool zone_balanced(struct zone *zone, int order,
-                       unsigned long balance_gap, int classzone_idx)
+static bool zone_balanced(struct zone *zone, int order, int classzone_idx)
 {
-       unsigned long mark = high_wmark_pages(zone) + balance_gap;
+       unsigned long mark = high_wmark_pages(zone);
 
        return zone_watermark_ok_safe(zone, order, mark, classzone_idx);
 }
@@ -3007,7 +3004,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int 
order, long remaining,
                if (!populated_zone(zone))
                        continue;
 
-               if (zone_balanced(zone, order, 0, classzone_idx))
+               if (zone_balanced(zone, order, classzone_idx))
                        return true;
        }
 
@@ -3110,7 +3107,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int 
classzone_idx)
                                break;
                        }
 
-                       if (!zone_balanced(zone, order, 0, 0)) {
+                       if (!zone_balanced(zone, order, 0)) {
                                classzone_idx = i;
                                break;
                        } else {
@@ -3178,7 +3175,7 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int 
classzone_idx)
                        if (!populated_zone(zone))
                                continue;
 
-                       if (zone_balanced(zone, sc.order, 0, classzone_idx)) {
+                       if (zone_balanced(zone, sc.order, classzone_idx)) {
                                clear_bit(PGDAT_CONGESTED, &pgdat->flags);
                                clear_bit(PGDAT_DIRTY, &pgdat->flags);
                                goto out;
@@ -3389,7 +3386,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum 
zone_type classzone_idx)
        }
        if (!waitqueue_active(&pgdat->kswapd_wait))
                return;
-       if (zone_balanced(zone, order, 0, 0))
+       if (zone_balanced(zone, order, 0))
                return;
 
        trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
-- 
2.6.4