mm/page_alloc.c: simplify calculation of combined index of adjacent buddy lists
The previous approach of calucation of combined index was
page_idx & ~(1 << order))
but we have same result with
page_idx & buddy_idx
This reduces instructions slightly as well as enhances readability.
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix used-unintialised warning]
Signed-off-by: KyongHo Cho <pullip.cho@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9dfe49b..bda1db3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -427,18 +427,10 @@
*
* Assumption: *_mem_map is contiguous at least up to MAX_ORDER
*/
-static inline struct page *
-__page_find_buddy(struct page *page, unsigned long page_idx, unsigned int order)
-{
- unsigned long buddy_idx = page_idx ^ (1 << order);
-
- return page + (buddy_idx - page_idx);
-}
-
static inline unsigned long
-__find_combined_index(unsigned long page_idx, unsigned int order)
+__find_buddy_index(unsigned long page_idx, unsigned int order)
{
- return (page_idx & ~(1 << order));
+ return page_idx ^ (1 << order);
}
/*
@@ -500,6 +492,7 @@
{
unsigned long page_idx;
unsigned long combined_idx;
+ unsigned long uninitialized_var(buddy_idx);
struct page *buddy;
if (unlikely(PageCompound(page)))
@@ -514,7 +507,8 @@
VM_BUG_ON(bad_range(zone, page));
while (order < MAX_ORDER-1) {
- buddy = __page_find_buddy(page, page_idx, order);
+ buddy_idx = __find_buddy_index(page_idx, order);
+ buddy = page + (buddy_idx - page_idx);
if (!page_is_buddy(page, buddy, order))
break;
@@ -522,7 +516,7 @@
list_del(&buddy->lru);
zone->free_area[order].nr_free--;
rmv_page_order(buddy);
- combined_idx = __find_combined_index(page_idx, order);
+ combined_idx = buddy_idx & page_idx;
page = page + (combined_idx - page_idx);
page_idx = combined_idx;
order++;
@@ -539,9 +533,10 @@
*/
if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) {
struct page *higher_page, *higher_buddy;
- combined_idx = __find_combined_index(page_idx, order);
- higher_page = page + combined_idx - page_idx;
- higher_buddy = __page_find_buddy(higher_page, combined_idx, order + 1);
+ combined_idx = buddy_idx & page_idx;
+ higher_page = page + (combined_idx - page_idx);
+ buddy_idx = __find_buddy_index(combined_idx, order + 1);
+ higher_buddy = 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]);