On 10/31/2014 08:25 AM, Joonsoo Kim wrote:
@@ -571,6 +548,7 @@ static inline void __free_one_page(struct page *page,
unsigned long combined_idx;
unsigned long uninitialized_var(buddy_idx);
struct page *buddy;
+ int max_order = MAX_ORDER;
VM_BUG_ON(!zone_is_initialized(zone));
@@ -579,15 +557,23 @@ static inline void __free_one_page(struct page *page,
return;
VM_BUG_ON(migratetype == -1);
- if (!is_migrate_isolate(migratetype))
+ if (is_migrate_isolate(migratetype)) {
+ /*
+ * We restrict max order of merging to prevent merge
+ * between freepages on isolate pageblock and normal
+ * pageblock. Without this, pageblock isolation
+ * could cause incorrect freepage accounting.
+ */
+ max_order = min(MAX_ORDER, pageblock_order + 1);
+ } else
__mod_zone_freepage_state(zone, 1 << order, migratetype);
Please add { } to the else branch, this looks ugly :)
- page_idx = pfn & ((1 << MAX_ORDER) - 1);
+ page_idx = pfn & ((1 << max_order) - 1);
VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page);
VM_BUG_ON_PAGE(bad_range(zone, page), page);
- while (order < MAX_ORDER-1) {
+ while (order < max_order - 1) {
buddy_idx = __find_buddy_index(page_idx, order);
buddy = page + (buddy_idx - page_idx);
if (!page_is_buddy(page, buddy, order))
@@ -1590,7 +1576,7 @@ void split_page(struct page *page, unsigned int order)
}
EXPORT_SYMBOL_GPL(split_page);
-static int __isolate_free_page(struct page *page, unsigned int order)
+int __isolate_free_page(struct page *page, unsigned int order)
{
unsigned long watermark;
struct zone *zone;
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 1fa4a4d..df61c93 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -76,17 +76,48 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype)
{
struct zone *zone;
unsigned long flags, nr_pages;
+ struct page *isolated_page = NULL;
+ unsigned int order;
+ unsigned long page_idx, buddy_idx;
+ struct page *buddy;
+ int mt;
zone = page_zone(page);
spin_lock_irqsave(&zone->lock, flags);
if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
goto out;
+
+ /*
+ * Because freepage with more than pageblock_order on isolated
+ * pageblock is restricted to merge due to freepage counting problem,
+ * it is possible that there is free buddy page.
+ * move_freepages_block() doesn't care of merge so we need other
+ * approach in order to merge them. Isolation and free will make
+ * these pages to be merged.
+ */
+ if (PageBuddy(page)) {
+ order = page_order(page);
+ if (order >= pageblock_order) {
+ page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
+ buddy_idx = __find_buddy_index(page_idx, order);
+ buddy = page + (buddy_idx - page_idx);
+ mt = get_pageblock_migratetype(buddy);
+
+ if (!is_migrate_isolate(mt)) {
You could use is_migrate_isolate_page(buddy) and save a variable.
+ __isolate_free_page(page, order);
+ set_page_refcounted(page);
+ isolated_page = page;
+ }
+ }
+ }
nr_pages = move_freepages_block(zone, page, migratetype);
- this is a costly no-op when the whole pageblock is an isolated page,
right?
__mod_zone_freepage_state(zone, nr_pages, migratetype);
- with isolated_page set, this means you increase freepage_state here,
and then the second time in __free_pages() below? __isolate_free_page()
won't decrease it as the pageblock is still MIGRATE_ISOLATE, so the net
result is overcounting?
set_pageblock_migratetype(page, migratetype);
zone->nr_isolate_pageblock--;
out:
spin_unlock_irqrestore(&zone->lock, flags);
+ if (isolated_page)
+ __free_pages(isolated_page, order);
}
static inline struct page *
--
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