[PATCH] mm: keep count of free areas

Keep track of the number of free pages of each order in the buddy allocator.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mmzone.h

@@ -23,6 +23,7 @@
 struct free_area {
 	struct list_head	free_list;
 	unsigned long		*map;
+	unsigned long		nr_free;
 };
 
 struct pglist_data;

mm/page_alloc.c

@@ -209,6 +209,7 @@ static inline void __free_pages_bulk (struct page *page, struct page *base,
 		BUG_ON(bad_range(zone, buddy1));
 		BUG_ON(bad_range(zone, buddy2));
 		list_del(&buddy1->lru);
+		area->nr_free--;
 		mask <<= 1;
 		order++;
 		area++;
@@ -216,6 +217,7 @@ static inline void __free_pages_bulk (struct page *page, struct page *base,
 		page_idx &= mask;
 	}
 	list_add(&(base + page_idx)->lru, &area->free_list);
+	area->nr_free++;
 }
 
 static inline void free_pages_check(const char *function, struct page *page)
@@ -317,6 +319,7 @@ expand(struct zone *zone, struct page *page,
 		size >>= 1;
 		BUG_ON(bad_range(zone, &page[size]));
 		list_add(&page[size].lru, &area->free_list);
+		area->nr_free++;
 		MARK_USED(index + size, high, area);
 	}
 	return page;
@@ -380,6 +383,7 @@ static struct page *__rmqueue(struct zone *zone, unsigned int order)
 
 		page = list_entry(area->free_list.next, struct page, lru);
 		list_del(&page->lru);
+		area->nr_free--;
 		index = page - zone->zone_mem_map;
 		if (current_order != MAX_ORDER-1)
 			MARK_USED(index, current_order, area);
@@ -1124,7 +1128,6 @@ void show_free_areas(void)
 	}
 
 	for_each_zone(zone) {
-		struct list_head *elem;
  		unsigned long nr, flags, order, total = 0;
 
 		show_node(zone);
@@ -1136,9 +1139,7 @@ void show_free_areas(void)
 
 		spin_lock_irqsave(&zone->lock, flags);
 		for (order = 0; order < MAX_ORDER; order++) {
-			nr = 0;
-			list_for_each(elem, &zone->free_area[order].free_list)
-				++nr;
+			nr = zone->free_area[order].nr_free;
 			total += nr << order;
 			printk("%lu*%lukB ", nr, K(1UL) << order);
 		}
@@ -1470,6 +1471,7 @@ void zone_init_free_lists(struct pglist_data *pgdat, struct zone *zone, unsigned
 		bitmap_size = pages_to_bitmap_size(order, size);
 		zone->free_area[order].map =
 		  (unsigned long *) alloc_bootmem_node(pgdat, bitmap_size);
+		zone->free_area[order].nr_free = 0;
 	}
 }
 
@@ -1657,8 +1659,7 @@ static void frag_stop(struct seq_file *m, void *arg)
 }
 
 /* 
- * This walks the freelist for each zone. Whilst this is slow, I'd rather 
- * be slow here than slow down the fast path by keeping stats - mjbligh
+ * This walks the free areas for each zone.
  */
 static int frag_show(struct seq_file *m, void *arg)
 {
@@ -1674,14 +1675,8 @@ static int frag_show(struct seq_file *m, void *arg)
 
 		spin_lock_irqsave(&zone->lock, flags);
 		seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
-		for (order = 0; order < MAX_ORDER; ++order) {
-			unsigned long nr_bufs = 0;
-			struct list_head *elem;
-
-			list_for_each(elem, &(zone->free_area[order].free_list))
-				++nr_bufs;
-			seq_printf(m, "%6lu ", nr_bufs);
-		}
+		for (order = 0; order < MAX_ORDER; ++order)
+			seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
 		spin_unlock_irqrestore(&zone->lock, flags);
 		seq_putc(m, '\n');
 	}