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mm/page_alloc.c: simplify calculation of combined index of adjacent buddy lists

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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>
This commit is contained in:
KyongHo Cho 2011-01-13 15:47:24 -08:00 committed by Linus Torvalds
parent 5520e89485
commit 43506fad21
1 changed files with 10 additions and 15 deletions
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25
mm/page_alloc.c
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@ -427,18 +427,10 @@ static inline void rmv_page_order(struct page *page)
* *
* Assumption: *_mem_map is contiguous at least up to MAX_ORDER * 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 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 page_idx;
unsigned long combined_idx; unsigned long combined_idx;
unsigned long uninitialized_var(buddy_idx);
struct page *buddy; struct page *buddy;
if (unlikely(PageCompound(page))) if (unlikely(PageCompound(page)))
@ -514,7 +507,8 @@ static inline void __free_one_page(struct page *page,
VM_BUG_ON(bad_range(zone, page)); VM_BUG_ON(bad_range(zone, page));
while (order < MAX_ORDER-1) { 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)) if (!page_is_buddy(page, buddy, order))
break; break;
@ -522,7 +516,7 @@ static inline void __free_one_page(struct page *page,
list_del(&buddy->lru); list_del(&buddy->lru);
zone->free_area[order].nr_free--; zone->free_area[order].nr_free--;
rmv_page_order(buddy); 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 = page + (combined_idx - page_idx);
page_idx = combined_idx; page_idx = combined_idx;
order++; 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))) { if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) {
struct page *higher_page, *higher_buddy; struct page *higher_page, *higher_buddy;
combined_idx = __find_combined_index(page_idx, order); combined_idx = buddy_idx & page_idx;
higher_page = page + combined_idx - page_idx; higher_page = page + (combined_idx - page_idx);
higher_buddy = __page_find_buddy(higher_page, combined_idx, order + 1); 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)) { if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
list_add_tail(&page->lru, list_add_tail(&page->lru,
&zone->free_area[order].free_list[migratetype]); &zone->free_area[order].free_list[migratetype]);