[RFC PATCH 05/11] mm: Propogate Treated bit when splitting

Alexander Duyck
2019-05-30T21:54:17Z

When we are going to call "expand" to split a page into subpages we should
mark those subpages as being "Treated" if the parent page was a "Treated"
page. By doing this we can avoid potentially providing hints on a page that
was already hinted at a larger page size as being unused.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
include/linux/mmzone.h | 8 ++++++--
mm/page_alloc.c | 18 +++++++++++++++---
2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 988c3094b686..a55fe6d2f63c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -97,16 +97,20 @@ struct free_area {
static inline void add_to_free_area(struct page *page, struct free_area *area,
int migratetype)
{
+ if (PageTreated(page))
+ area->nr_free_treated++;
+ else
+ area->nr_free_raw++;
+
list_add(&page->lru, &area->free_list[migratetype]);
- area->nr_free_raw++;
}

/* Used for pages not on another list */
static inline void add_to_free_area_tail(struct page *page, struct free_area *area,
int migratetype)
{
- list_add_tail(&page->lru, &area->free_list[migratetype]);
area->nr_free_raw++;
+ list_add_tail(&page->lru, &area->free_list[migratetype]);
}

/* Used for pages which are on another list */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 10eaea762627..f6c067c6c784 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1965,7 +1965,7 @@ void __init init_cma_reserved_pageblock(struct page *page)
*/
static inline void expand(struct zone *zone, struct page *page,
int low, int high, struct free_area *area,
- int migratetype)
+ int migratetype, bool treated)
{
unsigned long size = 1 << high;

@@ -1984,8 +1984,17 @@ static inline void expand(struct zone *zone, struct page *page,
if (set_page_guard(zone, &page[size], high, migratetype))
continue;

- add_to_free_area(&page[size], area, migratetype);
set_page_order(&page[size], high);
+ if (treated)
+ __SetPageTreated(&page[size]);
+
+ /*
+ * The list we are placing this page in should be empty
+ * so it should be safe to place it here without worrying
+ * about creating a block of raw pages floating in between
+ * two blocks of treated pages.
+ */
+ add_to_free_area(&page[size], area, migratetype);
}
}

@@ -2122,6 +2131,7 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
unsigned int current_order;
struct free_area *area;
struct page *page;
+ bool treated;

/* Find a page of the appropriate size in the preferred list */
for (current_order = order; current_order < MAX_ORDER; ++current_order) {
@@ -2129,8 +2139,10 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
page = get_page_from_free_area(area, migratetype);
if (!page)
continue;
+ treated = PageTreated(page);
del_page_from_free_area(page, area);
- expand(zone, page, order, current_order, area, migratetype);
+ expand(zone, page, order, current_order, area, migratetype,
+ treated);
set_pcppage_migratetype(page, migratetype);
return page;
}