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

Mel Gorman
2016-06-09T18:06:40Z

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 <mgorman@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