[RFC PATCH v2 05/15] mm: Add data-structures to describe memory regions within the zones' freelists

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

In order to influence page allocation decisions (i.e., to make page-allocation
region-aware), we need to be able to distinguish pageblocks belonging to
different zone memory regions within the zones' (buddy) freelists.

So, within every freelist in a zone, provide pointers to describe the
boundaries of zone memory regions and counters to track the number of free
pageblocks within each region.

Also, fixup the references to the freelist's list_head inside struct free_area.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---

 include/linux/mmzone.h |   17 ++++++++++++++++-
 mm/compaction.c        |    2 +-
 mm/page_alloc.c        |   23 ++++++++++++-----------
 mm/vmstat.c            |    2 +-
 4 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f772e05..76667bf 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -83,8 +83,23 @@ static inline int get_pageblock_migratetype(struct page *page)
 	return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
 }
 
+struct mem_region_list {
+	struct list_head	*page_block;
+	unsigned long		nr_free;
+};
+
+struct free_list {
+	struct list_head	list;
+
+	/*
+	 * Demarcates pageblocks belonging to different regions within
+	 * this freelist.
+	 */
+	struct mem_region_list	mr_list[MAX_NR_ZONE_REGIONS];
+};
+
 struct free_area {
-	struct list_head	free_list[MIGRATE_TYPES];
+	struct free_list	free_list[MIGRATE_TYPES];
 	unsigned long		nr_free;
 };
 
diff --git a/mm/compaction.c b/mm/compaction.c
index 05ccb4c..13912f5 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -858,7 +858,7 @@ static int compact_finished(struct zone *zone,
 		struct free_area *area = &zone->free_area[order];
 
 		/* Job done if page is free of the right migratetype */
-		if (!list_empty(&area->free_list[cc->migratetype]))
+		if (!list_empty(&area->free_list[cc->migratetype].list))
 			return COMPACT_PARTIAL;
 
 		/* Job done if allocation would set block type */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index af87471..963de6c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -593,12 +593,13 @@ static inline void __free_one_page(struct page *page,
 		higher_buddy = higher_page + (buddy_idx - combined_idx);
 		if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
 			list_add_tail(&page->lru,
-				&zone->free_area[order].free_list[migratetype]);
+				&zone->free_area[order].free_list[migratetype].list);
 			goto out;
 		}
 	}
 
-	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
+	list_add(&page->lru,
+		&zone->free_area[order].free_list[migratetype].list);
 out:
 	zone->free_area[order].nr_free++;
 }
@@ -831,7 +832,7 @@ static inline void expand(struct zone *zone, struct page *page,
 			continue;
 		}
 #endif
-		list_add(&page[size].lru, &area->free_list[migratetype]);
+		list_add(&page[size].lru, &area->free_list[migratetype].list);
 		area->nr_free++;
 		set_page_order(&page[size], high);
 	}
@@ -893,10 +894,10 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
 	/* Find a page of the appropriate size in the preferred list */
 	for (current_order = order; current_order < MAX_ORDER; ++current_order) {
 		area = &(zone->free_area[current_order]);
-		if (list_empty(&area->free_list[migratetype]))
+		if (list_empty(&area->free_list[migratetype].list))
 			continue;
 
-		page = list_entry(area->free_list[migratetype].next,
+		page = list_entry(area->free_list[migratetype].list.next,
 							struct page, lru);
 		list_del(&page->lru);
 		rmv_page_order(page);
@@ -968,7 +969,7 @@ int move_freepages(struct zone *zone,
 
 		order = page_order(page);
 		list_move(&page->lru,
-			  &zone->free_area[order].free_list[migratetype]);
+			  &zone->free_area[order].free_list[migratetype].list);
 		set_freepage_migratetype(page, migratetype);
 		page += 1 << order;
 		pages_moved += 1 << order;
@@ -1029,10 +1030,10 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
 				break;
 
 			area = &(zone->free_area[current_order]);
-			if (list_empty(&area->free_list[migratetype]))
+			if (list_empty(&area->free_list[migratetype].list))
 				continue;
 
-			page = list_entry(area->free_list[migratetype].next,
+			page = list_entry(area->free_list[migratetype].list.next,
 					struct page, lru);
 			area->nr_free--;
 
@@ -1296,7 +1297,7 @@ void mark_free_pages(struct zone *zone)
 		}
 
 	for_each_migratetype_order(order, t) {
-		list_for_each(curr, &zone->free_area[order].free_list[t]) {
+		list_for_each(curr, &zone->free_area[order].free_list[t].list) {
 			unsigned long i;
 
 			pfn = page_to_pfn(list_entry(curr, struct page, lru));
@@ -3092,7 +3093,7 @@ void show_free_areas(unsigned int filter)
 
 			types[order] = 0;
 			for (type = 0; type < MIGRATE_TYPES; type++) {
-				if (!list_empty(&area->free_list[type]))
+				if (!list_empty(&area->free_list[type].list))
 					types[order] |= 1 << type;
 			}
 		}
@@ -3944,7 +3945,7 @@ static void __meminit zone_init_free_lists(struct zone *zone)
 {
 	int order, t;
 	for_each_migratetype_order(order, t) {
-		INIT_LIST_HEAD(&zone->free_area[order].free_list[t]);
+		INIT_LIST_HEAD(&zone->free_area[order].free_list[t].list);
 		zone->free_area[order].nr_free = 0;
 	}
 }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index e1d8ed1..63e12f0 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -860,7 +860,7 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
 
 			area = &(zone->free_area[order]);
 
-			list_for_each(curr, &area->free_list[mtype])
+			list_for_each(curr, &area->free_list[mtype].list)
 				freecount++;
 			seq_printf(m, "%6lu ", freecount);
 		}

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