mmotm: Replace the watermark-related union in struct zone with a watermark[] array V3

index 7daf897..b7a78ad 100644
@@ -154,9 +154,9 @@ unsigned long __init zone_sizes_init(void)
 	 *  Use all area of internal RAM.
 	 *  see __alloc_pages()
 	 */
-	NODE_DATA(1)->node_zones->pages_min = 0;
-	NODE_DATA(1)->node_zones->pages_low = 0;
-	NODE_DATA(1)->node_zones->pages_high = 0;
+	NODE_DATA(1)->node_zones->watermark[WMARK_MIN] = 0;
+	NODE_DATA(1)->node_zones->watermark[WMARK_LOW] = 0;
+	NODE_DATA(1)->node_zones->watermark[WMARK_HIGH] = 0;
 
 	return holes;
 }

index 95a9257..4f99501 100644
@@ -163,6 +163,17 @@ static inline int is_unevictable_lru(enum lru_list l)
 #endif
 }
 
+enum zone_watermarks {
+	WMARK_MIN,
+	WMARK_LOW,
+	WMARK_HIGH,
+	NR_WMARK
+};
+
+#define min_wmark_pages(z) (z->watermark[WMARK_MIN])
+#define low_wmark_pages(z) (z->watermark[WMARK_LOW])
+#define high_wmark_pages(z) (z->watermark[WMARK_HIGH])
+
 struct per_cpu_pages {
 	int count;		/* number of pages in the list */
 	int high;		/* high watermark, emptying needed */

@@ -275,12 +286,9 @@ struct zone_reclaim_stat {
 
 struct zone {
 	/* Fields commonly accessed by the page allocator */
-	union {
-		struct {
-			unsigned long	pages_min, pages_low, pages_high;
-		};
-		unsigned long pages_mark[3];
-	};
+
+	/* zone watermarks, access with *_wmark_pages(zone) macros */
+	unsigned long watermark[NR_WMARK];
 
 	/*
 	 * We don't know if the memory that we're going to allocate will be freeable

110 lines not on this page · raw message

index 822056c..462ced1 100644
@@ -1437,7 +1437,7 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc,
 		free  = zone_page_state(zone, NR_FREE_PAGES);
 		/* If we have very few page cache pages,
 		   force-scan anon pages. */
-		if (unlikely(file + free <= zone->pages_high)) {
+		if (unlikely(file + free <= high_wmark_pages(zone))) {
 			percent[0] = 100;
 			percent[1] = 0;
 			return;

@@ -1586,11 +1586,13 @@ static void shrink_zone(int priority, struct zone *zone,
  * try to reclaim pages from zones which will satisfy the caller's allocation
  * request.
  *
- * We reclaim from a zone even if that zone is over pages_high.  Because:
+ * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
+ * Because:
  * a) The caller may be trying to free *extra* pages to satisfy a higher-order
  *    allocation or
- * b) The zones may be over pages_high but they must go *over* pages_high to
- *    satisfy the `incremental min' zone defense algorithm.
+ * b) The target zone may be at high_wmark_pages(zone) but the lower zones
+ *    must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
+ *    zone defense algorithm.
  *
  * If a zone is deemed to be full of pinned pages then just give it a light
  * scan then give up on it.

@@ -1796,7 +1798,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
 
 /*
  * For kswapd, balance_pgdat() will work across all this node's zones until
- * they are all at pages_high.
+ * they are all at high_wmark_pages(zone).
  *
  * Returns the number of pages which were actually freed.
  *

@@ -1809,11 +1811,11 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
  * the zone for when the problem goes away.
  *
  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
- * zones which have free_pages > pages_high, but once a zone is found to have
- * free_pages <= pages_high, we scan that zone and the lower zones regardless
- * of the number of free pages in the lower zones.  This interoperates with
- * the page allocator fallback scheme to ensure that aging of pages is balanced
- * across the zones.
+ * zones which have free_pages > high_wmark_pages(zone), but once a zone is
+ * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
+ * lower zones regardless of the number of free pages in the lower zones. This
+ * interoperates with the page allocator fallback scheme to ensure that aging
+ * of pages is balanced across the zones.
  */
 static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
 {

@@ -1834,7 +1836,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
 	};
 	/*
 	 * temp_priority is used to remember the scanning priority at which
-	 * this zone was successfully refilled to free_pages == pages_high.
+	 * this zone was successfully refilled to
+	 * free_pages == high_wmark_pages(zone).
 	 */
 	int temp_priority[MAX_NR_ZONES];
 

@@ -1879,8 +1882,8 @@ loop_again:
 				shrink_active_list(SWAP_CLUSTER_MAX, zone,
 							&sc, priority, 0);
 
-			if (!zone_watermark_ok(zone, order, zone->pages_high,
-					       0, 0)) {
+			if (!zone_watermark_ok(zone, order,
+					high_wmark_pages(zone), 0, 0)) {
 				end_zone = i;
 				break;
 			}

@@ -1914,8 +1917,8 @@ loop_again:
 					priority != DEF_PRIORITY)
 				continue;
 
-			if (!zone_watermark_ok(zone, order, zone->pages_high,
-					       end_zone, 0))
+			if (!zone_watermark_ok(zone, order,
+					high_wmark_pages(zone), end_zone, 0))
 				all_zones_ok = 0;
 			temp_priority[i] = priority;
 			sc.nr_scanned = 0;

@@ -1924,8 +1927,8 @@ loop_again:
 			 * We put equal pressure on every zone, unless one
 			 * zone has way too many pages free already.
 			 */
-			if (!zone_watermark_ok(zone, order, 8*zone->pages_high,
-						end_zone, 0))
+			if (!zone_watermark_ok(zone, order,
+					8*high_wmark_pages(zone), end_zone, 0))
 				shrink_zone(priority, zone, &sc);
 			reclaim_state->reclaimed_slab = 0;
 			nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL,

@@ -2091,7 +2094,7 @@ void wakeup_kswapd(struct zone *zone, int order)
 		return;
 
 	pgdat = zone->zone_pgdat;
-	if (zone_watermark_ok(zone, order, zone->pages_low, 0, 0))
+	if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
 		return;
 	if (pgdat->kswapd_max_order < order)
 		pgdat->kswapd_max_order = order;

index b42d06c..5e101d7 100644
@@ -725,9 +725,9 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		   "\n        spanned  %lu"
 		   "\n        present  %lu",
 		   zone_page_state(zone, NR_FREE_PAGES),
-		   zone->pages_min,
-		   zone->pages_low,
-		   zone->pages_high,
+		   min_wmark_pages(zone),
+		   low_wmark_pages(zone),
+		   high_wmark_pages(zone),
 		   zone->pages_scanned,
 		   zone->spanned_pages,
 		   zone->present_pages);