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mm: perform non-atomic test-clear of PG_mlocked on free

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By the time PG_mlocked is cleared in the page freeing path, nobody else is
looking at our page->flags anymore.

It is thus safe to make the test-and-clear non-atomic and thereby removing
an unnecessary and expensive operation from a hotpath.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2009-09-21 17:01:48 -07:00 committed by Linus Torvalds
parent bf88c8c83e
commit 451ea25da7
2 changed files with 11 additions and 5 deletions
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12
include/linux/page-flags.h
View file

@ -158,6 +158,9 @@ static inline int TestSetPage##uname(struct page *page) \
static inline int TestClearPage##uname(struct page *page) \ static inline int TestClearPage##uname(struct page *page) \
{ return test_and_clear_bit(PG_##lname, &page->flags); } { return test_and_clear_bit(PG_##lname, &page->flags); }
#define __TESTCLEARFLAG(uname, lname) \
static inline int __TestClearPage##uname(struct page *page) \
{ return __test_and_clear_bit(PG_##lname, &page->flags); }
#define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \ #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname) SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
@ -184,6 +187,9 @@ static inline void __ClearPage##uname(struct page *page) { }
#define TESTCLEARFLAG_FALSE(uname) \ #define TESTCLEARFLAG_FALSE(uname) \
static inline int TestClearPage##uname(struct page *page) { return 0; } static inline int TestClearPage##uname(struct page *page) { return 0; }
#define __TESTCLEARFLAG_FALSE(uname) \
static inline int __TestClearPage##uname(struct page *page) { return 0; }
struct page; /* forward declaration */ struct page; /* forward declaration */
TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked) TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
@ -250,11 +256,11 @@ PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT #ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
#define MLOCK_PAGES 1 #define MLOCK_PAGES 1
PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked) PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
TESTSCFLAG(Mlocked, mlocked) TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
#else #else
#define MLOCK_PAGES 0 #define MLOCK_PAGES 0
PAGEFLAG_FALSE(Mlocked) PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked) TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
#endif #endif
#ifdef CONFIG_ARCH_USES_PG_UNCACHED #ifdef CONFIG_ARCH_USES_PG_UNCACHED

4
mm/page_alloc.c
View file

@ -557,7 +557,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
unsigned long flags; unsigned long flags;
int i; int i;
int bad = 0; int bad = 0;
int wasMlocked = TestClearPageMlocked(page); int wasMlocked = __TestClearPageMlocked(page);
kmemcheck_free_shadow(page, order); kmemcheck_free_shadow(page, order);
@ -1026,7 +1026,7 @@ static void free_hot_cold_page(struct page *page, int cold)
struct zone *zone = page_zone(page); struct zone *zone = page_zone(page);
struct per_cpu_pages *pcp; struct per_cpu_pages *pcp;
unsigned long flags; unsigned long flags;
int wasMlocked = TestClearPageMlocked(page); int wasMlocked = __TestClearPageMlocked(page);
kmemcheck_free_shadow(page, 0); kmemcheck_free_shadow(page, 0);