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

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Date:   Thu, 30 May 2019 14:54:11 -0700
From:   Alexander Duyck <alexander.duyck@...il.com>
To:     nitesh@...hat.com, kvm@...r.kernel.org, david@...hat.com,
        mst@...hat.com, dave.hansen@...el.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     yang.zhang.wz@...il.com, pagupta@...hat.com, riel@...riel.com,
        konrad.wilk@...cle.com, lcapitulino@...hat.com,
        wei.w.wang@...el.com, aarcange@...hat.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, alexander.h.duyck@...ux.intel.com
Subject: [RFC PATCH 05/11] mm: Propogate Treated bit when splitting

From: Alexander Duyck <alexander.h.duyck@...ux.intel.com>

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@...ux.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;
 	}