The freelists for each migrate type can slowly become polluted due to the
per-cpu list. Consider what happens when the following happens
1. A 2^(MAX_ORDER-1) list is reserved for __GFP_MOVABLE pages
2. An order-0 page is allocated from the newly reserved block
3. The page is freed and placed on the per-cpu list
4. alloc_page() is called with GFP_KERNEL as the gfp_mask
5. The per-cpu list is used to satisfy the allocation
This results in a kernel page is in the middle of a migratable region. This
patch prevents this leak occuring by storing the MIGRATE_ type of the page in
page->private. On allocate, a page will only be returned of the desired type,
else more pages will be allocated. This may temporarily allow a per-cpu list
to go over the pcp->high limit but it'll be corrected on the next free. Care
is taken to preserve the hotness of pages recently freed.
Signed-off-by: Mel Gorman <[email protected]>
---
page_alloc.c | 34 ++++++++++++++++++++++++++++------
1 files changed, 28 insertions(+), 6 deletions(-)
diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.19-rc5-mm2-003_clustering_core/mm/page_alloc.c linux-2.6.19-rc5-mm2-004_percpu/mm/page_alloc.c
--- linux-2.6.19-rc5-mm2-003_clustering_core/mm/page_alloc.c 2006-11-21 10:48:55.000000000 +0000
+++ linux-2.6.19-rc5-mm2-004_percpu/mm/page_alloc.c 2006-11-21 10:50:40.000000000 +0000
@@ -415,6 +415,7 @@ static inline void __free_one_page(struc
{
unsigned long page_idx;
int order_size = 1 << order;
+ int migratetype = get_page_migratetype(page);
if (unlikely(PageCompound(page)))
destroy_compound_page(page, order);
@@ -449,8 +450,7 @@ static inline void __free_one_page(struc
order++;
}
set_page_order(page, order);
- list_add(&page->lru,
- &zone->free_area[order].free_list[get_page_migratetype(page)]);
+ list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
zone->free_area[order].nr_free++;
}
@@ -738,7 +738,8 @@ static int rmqueue_bulk(struct zone *zon
struct page *page = __rmqueue(zone, order, migratetype);
if (unlikely(page == NULL))
break;
- list_add_tail(&page->lru, list);
+ list_add(&page->lru, list);
+ set_page_private(page, migratetype);
}
spin_unlock(&zone->lock);
return i;
@@ -876,6 +877,7 @@ static void fastcall free_hot_cold_page(
local_irq_save(flags);
__count_vm_event(PGFREE);
list_add(&page->lru, &pcp->list);
+ set_page_private(page, get_page_migratetype(page));
pcp->count++;
if (pcp->count >= pcp->high) {
free_pages_bulk(zone, pcp->batch, &pcp->list, 0);
@@ -940,9 +942,29 @@ again:
if (unlikely(!pcp->count))
goto failed;
}
- page = list_entry(pcp->list.next, struct page, lru);
- list_del(&page->lru);
- pcp->count--;
+
+ /* Find a page of the appropriate migrate type */
+ list_for_each_entry(page, &pcp->list, lru) {
+ if (page_private(page) == migratetype) {
+ list_del(&page->lru);
+ pcp->count--;
+ break;
+ }
+ }
+
+ /*
+ * Check if a page of the appropriate migrate type
+ * was found. If not, allocate more to the pcp list
+ */
+ if (&page->lru == &pcp->list) {
+ pcp->count += rmqueue_bulk(zone, 0,
+ pcp->batch, &pcp->list, migratetype);
+ page = list_entry(pcp->list.next, struct page, lru);
+ VM_BUG_ON(page_private(page) != migratetype);
+ list_del(&page->lru);
+ pcp->count--;
+ }
+
} else {
spin_lock_irqsave(&zone->lock, flags);
page = __rmqueue(zone, order, migratetype);
-
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