[PATCH 4/9] defrag helper functions

Joel Schopp
2005-09-26T20:08:39Z

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This patch contains a handful of trivial functions, and one fairly short function
that finds an unallocated 2^MAX_ORDER-1 sized block from one type and moves it
to another type.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>

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Index: 2.6.13-joel2/mm/page_alloc.c
===================================================================
--- 2.6.13-joel2.orig/mm/page_alloc.c 2005-09-20 13:45:47.%N -0500
+++ 2.6.13-joel2/mm/page_alloc.c 2005-09-20 14:16:35.%N -0500
@@ -63,7 +63,62 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_Z

EXPORT_SYMBOL(totalram_pages);
EXPORT_SYMBOL(nr_swap_pages);
+static inline int need_min_fallback_reserve(struct zone *zone)
+{
+ return (zone->free_pages >> MAX_ORDER) < zone->fallback_reserve;
+}
+static inline int is_min_fallback_reserved(struct zone *zone)
+{
+ return zone->fallback_balance < 0;
+}
+static inline unsigned int get_pageblock_type(struct zone *zone,
+ struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+ int i, bitidx;
+ unsigned int type = 0;
+ unsigned long *usemap;
+
+ bitidx = pfn_to_bitidx(zone, pfn);
+ usemap = pfn_to_usemap(zone, pfn);
+
+ for (i=0; i < BITS_PER_RCLM_TYPE; i++) {
+ type = (type << 1);
+ type |= (!!test_bit(bitidx+i, usemap));
+ }
+
+ return type;
+}

+void assign_bit(int bit_nr, unsigned long* map, int value)
+{
+ switch (value) {
+ case 0:
+ clear_bit(bit_nr, map);
+ break;
+ default:
+ set_bit(bit_nr, map);
+ }
+}
+/*
+ * Reserve a block of pages for an allocation type & enforce function
+ * being changed if more bits are added to keep track of additional types
+ */
+BUILD_BUG_ON(BITS_PER_RCLM_TYPE > 2)
+static inline void set_pageblock_type(struct zone *zone, struct page *page,
+ int type)
+{
+ unsigned long pfn = page_to_pfn(page);
+ int bitidx;
+ unsigned long *usemap;
+
+ usemap = pfn_to_usemap(zone, pfn);
+ bitidx = pfn_to_bitidx(zone, pfn);
+
+ assign_bit(bitidx, usemap, (type & 0x1));
+ assign_bit(bitidx + 1, usemap, (type & 0x2));
+
+}
/*
* Used by page_zone() to look up the address of the struct zone whose
* id is encoded in the upper bits of page->flags
@@ -465,6 +520,41 @@ static void prep_new_page(struct page *p
kernel_map_pages(page, 1 << order, 1);
}

+/*
+ * Find a list that has a 2^MAX_ORDER-1 block of pages available and
+ * return it
+ */
+static inline struct page* steal_largepage(struct zone *zone, int alloctype)
+{
+ struct page *page;
+ struct free_area *area;
+ int i=0;
+
+ for(i = 0; i < RCLM_TYPES; i++) {
+ if(i == alloctype)
+ continue;
+
+ area = &zone->free_area_lists[i][MAX_ORDER-1];
+ if(!list_empty(&area->free_list))
+ break;
+ }
+ if (i == RCLM_TYPES) return NULL;
+
+ page = list_entry(area->free_list.next, struct page, lru);
+ area->nr_free--;
+
+ if (!is_min_fallback_reserved(zone) &&
+ need_min_fallback_reserve(zone)) {
+ alloctype = RCLM_FALLBACK;
+ }
+
+ set_pageblock_type(zone, page, alloctype);
+ dec_reserve_count(zone, i);
+ inc_reserve_count(zone, alloctype);
+
+ return page;
+}
+
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.