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mm: pagecache insertion fewer atomics

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Setting and clearing the page locked when inserting it into swapcache /
pagecache when it has no other references can use non-atomic page flags
operations because no other CPU may be operating on it at this time.

This saves one atomic operation when inserting a page into pagecache.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2008-10-18 20:26:57 -07:00 committed by Linus Torvalds
parent 9978ad583e
commit f45840b5c1
2 changed files with 9 additions and 9 deletions
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14
include/linux/pagemap.h
View file

@ -299,14 +299,14 @@ extern int __lock_page_killable(struct page *page);
extern void __lock_page_nosync(struct page *page);
extern void unlock_page(struct page *page);
static inline void set_page_locked(struct page *page)
static inline void __set_page_locked(struct page *page)
{
set_bit(PG_locked, &page->flags);
__set_bit(PG_locked, &page->flags);
}
static inline void clear_page_locked(struct page *page)
static inline void __clear_page_locked(struct page *page)
{
clear_bit(PG_locked, &page->flags);
__clear_bit(PG_locked, &page->flags);
}
static inline int trylock_page(struct page *page)
@ -438,17 +438,17 @@ extern void __remove_from_page_cache(struct page *page);
/*
* Like add_to_page_cache_locked, but used to add newly allocated pages:
* the page is new, so we can just run set_page_locked() against it.
* the page is new, so we can just run __set_page_locked() against it.
*/
static inline int add_to_page_cache(struct page *page,
struct address_space *mapping, pgoff_t offset, gfp_t gfp_mask)
{
int error;
set_page_locked(page);
__set_page_locked(page);
error = add_to_page_cache_locked(page, mapping, offset, gfp_mask);
if (unlikely(error))
clear_page_locked(page);
__clear_page_locked(page);
return error;
}

4
mm/swap_state.c
View file

@ -303,7 +303,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
* re-using the just freed swap entry for an existing page.
* May fail (-ENOMEM) if radix-tree node allocation failed.
*/
set_page_locked(new_page);
__set_page_locked(new_page);
SetPageSwapBacked(new_page);
err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
if (likely(!err)) {
@ -315,7 +315,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
return new_page;
}
ClearPageSwapBacked(new_page);
clear_page_locked(new_page);
__clear_page_locked(new_page);
swap_free(entry);
} while (err != -ENOMEM);