The kswapd reclaim has had one single goal:
reclaim from zones to make their watermarks ok.
Now add another weak goal(it will not set all_zones_ok=0):
reclaim from the least aged zone to help balance the aging rates.
Two major aspects of this algorithm:
- reclaim the least aged zone unless it catches up with the most aged zone
- reclaim for weaker watermark by calling watermark_ok() with classzone_idx=0
That garuantees reclaims-for-aging to be more than reclaims-for-watermark if
there is ever a big imbalance, thus eliminates the chance of growing gaps.
Signed-off-by: Wu Fengguang <[email protected]>
---
mm/vmscan.c | 39 ++++++++++++++++++++++++++++++---------
1 files changed, 30 insertions(+), 9 deletions(-)
--- linux.orig/mm/vmscan.c
+++ linux/mm/vmscan.c
@@ -1356,6 +1356,8 @@ static int balance_pgdat(pg_data_t *pgda
int total_scanned, total_reclaimed;
struct reclaim_state *reclaim_state = current->reclaim_state;
struct scan_control sc;
+ struct zone *youngest_zone = NULL;
+ struct zone *oldest_zone = NULL;
loop_again:
total_scanned = 0;
@@ -1371,11 +1373,20 @@ loop_again:
struct zone *zone = pgdat->node_zones + i;
zone->temp_priority = DEF_PRIORITY;
+
+ if (zone->present_pages == 0)
+ continue;
+
+ if (!oldest_zone)
+ youngest_zone = oldest_zone = zone;
+ else if (pages_more_aged(zone, oldest_zone))
+ oldest_zone = zone;
+ else if (pages_more_aged(youngest_zone, zone))
+ youngest_zone = zone;
}
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
unsigned long lru_pages = 0;
- int first_low_zone = 0;
all_zones_ok = 1;
sc.nr_scanned = 0;
@@ -1387,21 +1398,31 @@ loop_again:
if (!priority)
disable_swap_token();
- /* Scan in the highmem->dma direction */
- for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ /*
+ * Now scan the zone in the dma->highmem direction, stopping
+ * at the last zone which needs scanning.
+ *
+ * We do this because the page allocator works in the opposite
+ * direction. This prevents the page allocator from allocating
+ * pages behind kswapd's direction of progress, which would
+ * cause too much scanning of the lower zones.
+ */
+ for (i = 0; i < pgdat->nr_zones; i++) {
struct zone *zone = pgdat->node_zones + i;
if (!populated_zone(zone))
continue;
if (nr_pages == 0) { /* Not software suspend */
- if (zone_watermark_ok(zone, order,
- zone->pages_high, first_low_zone, 0))
+ if (!zone_watermark_ok(zone, order,
+ zone->pages_high,
+ 0, 0)) {
+ all_zones_ok = 0;
+ } else if (zone == youngest_zone &&
+ pages_more_aged(oldest_zone,
+ youngest_zone)) {
+ } else
continue;
-
- all_zones_ok = 0;
- if (first_low_zone < i)
- first_low_zone = i;
}
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
--