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Subject[PATCH 8/12] Move free pages between lists on steal
Date

When a fallback occurs, there will be free pages for one allocation type
stored on the list for another. When a large steal occurs, this patch will
move all the free pages within one list to the other.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
---

page_alloc.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++---
1 files changed, 62 insertions(+), 3 deletions(-)

diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.20-mm2-007_drainpercpu/mm/page_alloc.c linux-2.6.20-mm2-008_movefree/mm/page_alloc.c
--- linux-2.6.20-mm2-007_drainpercpu/mm/page_alloc.c 2007-02-20 18:35:52.000000000 +0000
+++ linux-2.6.20-mm2-008_movefree/mm/page_alloc.c 2007-02-20 18:38:07.000000000 +0000
@@ -682,6 +682,63 @@ static int fallbacks[MIGRATE_TYPES][MIGR
[MIGRATE_MOVABLE] = { MIGRATE_UNMOVABLE },
};

+/*
+ * Move the free pages in a range to the free lists of the requested type.
+ * Note that start_page and end_pages are not aligned in a MAX_ORDER_NR_PAGES
+ * boundary. If alignment is required, use move_freepages_block()
+ */
+int move_freepages(struct zone *zone,
+ struct page *start_page, struct page *end_page,
+ int migratetype)
+{
+ struct page *page;
+ unsigned long order;
+ int blocks_moved = 0;
+
+ BUG_ON(page_zone(start_page) != page_zone(end_page));
+
+ for (page = start_page; page < end_page;) {
+ if (!PageBuddy(page)) {
+ page++;
+ continue;
+ }
+#ifdef CONFIG_HOLES_IN_ZONE
+ if (!pfn_valid(page_to_pfn(page))) {
+ page++;
+ continue;
+ }
+#endif
+
+ order = page_order(page);
+ list_del(&page->lru);
+ list_add(&page->lru,
+ &zone->free_area[order].free_list[migratetype]);
+ page += 1 << order;
+ blocks_moved++;
+ }
+
+ return blocks_moved;
+}
+
+int move_freepages_block(struct zone *zone, struct page *page, int migratetype)
+{
+ unsigned long start_pfn;
+ struct page *start_page, *end_page;
+
+ start_pfn = page_to_pfn(page);
+ start_pfn = start_pfn & ~(MAX_ORDER_NR_PAGES-1);
+ start_page = pfn_to_page(start_pfn);
+ end_page = start_page + MAX_ORDER_NR_PAGES;
+
+ /* Do not cross zone boundaries */
+ if (page_zone(page) != page_zone(start_page))
+ start_page = page;
+ if (page_zone(page) != page_zone(end_page))
+ return 0;
+
+ return move_freepages(zone, start_page, end_page, migratetype);
+}
+
/* Remove an element from the buddy allocator from the fallback list */
static struct page *__rmqueue_fallback(struct zone *zone, int order,
int start_migratetype)
@@ -706,11 +763,13 @@ static struct page *__rmqueue_fallback(s
area->nr_free--;

/*
- * If breaking a large block of pages, place the buddies
- * on the preferred allocation list
+ * If breaking a large block of pages, move all free
+ * pages to the preferred allocation list
*/
- if (unlikely(current_order >= MAX_ORDER / 2))
+ if (unlikely(current_order >= MAX_ORDER / 2)) {
migratetype = start_migratetype;
+ move_freepages_block(zone, page, migratetype);
+ }

/* Remove the page from the freelists */
list_del(&page->lru);
-
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