[RFC PATCH v4 19/40] mm: Provide a mechanism to release free memory to the region allocator

["Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>]

Implement helper functions to release freepages from the buddy freelists to
the region allocator.

For simplicity, all operations related to the region allocator are performed
at the granularity of entire memory regions. That is, when we release freepages
to the region allocator, we free all the pages belonging to that region.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
---

 mm/page_alloc.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d96746e..c727bba 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -919,6 +919,26 @@ static void move_page_freelist(struct page *page, struct free_list *old_list,
 	add_to_freelist(page, new_list, order);
 }
 
+/* Add pages from the given buddy freelist to the region allocator */
+static void add_to_region_allocator(struct zone *z, struct free_list *free_list,
+				    int region_id)
+{
+	struct region_allocator *reg_alloc;
+	struct list_head *ralloc_list;
+	int order;
+
+	if (WARN_ON(list_empty(&free_list->list)))
+		return;
+
+	order = page_order(list_first_entry(&free_list->list,
+					    struct page, lru));
+
+	reg_alloc = &z->region_allocator;
+	ralloc_list = &reg_alloc->region[region_id].region_area[order].list;
+
+	del_from_freelist_bulk(ralloc_list, free_list, order, region_id);
+}
+
 /*
  * Freeing function for a buddy system allocator.
  *

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