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Commit 43506fad authored by KyongHo Cho's avatar KyongHo Cho Committed by Linus Torvalds
Browse files

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: default avatarKyongHo Cho <pullip.cho@samsung.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5520e894

mm/page_alloc.c

+10 −15
Original line number Diff line number Diff line
@@ -427,18 +427,10 @@ static inline void rmv_page_order(struct page *page) 
 *

 * 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 @@ static inline void __free_one_page(struct page *page, 
{

	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 @@ static inline void __free_one_page(struct page *page, 
	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 @@ static inline void __free_one_page(struct page *page, 
		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 @@ static inline void __free_one_page(struct page *page, 
	 */

	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]);