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authorJohannes Weiner <hannes@cmpxchg.org>2009-09-21 17:01:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-09-22 07:17:30 -0700
commit451ea25da71590361c71bf3044c55b870a887d53 (patch)
treee2e9de6e7c1fb4f79c0413a3c4d401ec9263b722
parentbf88c8c83e4425d17e29daa5354ffb1f8ba7b225 (diff)
mm: perform non-atomic test-clear of PG_mlocked on free
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>
-rw-r--r--include/linux/page-flags.h12
-rw-r--r--mm/page_alloc.c4
2 files changed, 11 insertions, 5 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 2b87acfc5f8..d07c0bb2203 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -158,6 +158,9 @@ static inline int TestSetPage##uname(struct page *page) \
static inline int TestClearPage##uname(struct page *page) \
{ 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) \
SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
@@ -184,6 +187,9 @@ static inline void __ClearPage##uname(struct page *page) { }
#define TESTCLEARFLAG_FALSE(uname) \
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 */
TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
@@ -250,11 +256,11 @@ PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable)
#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
#define MLOCK_PAGES 1
PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked)
- TESTSCFLAG(Mlocked, mlocked)
+ TESTSCFLAG(Mlocked, mlocked) __TESTCLEARFLAG(Mlocked, mlocked)
#else
#define MLOCK_PAGES 0
-PAGEFLAG_FALSE(Mlocked)
- SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
+PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked)
+ TESTCLEARFLAG_FALSE(Mlocked) __TESTCLEARFLAG_FALSE(Mlocked)
#endif
#ifdef CONFIG_ARCH_USES_PG_UNCACHED
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 81926c7ef6f..9242d13f4ff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -557,7 +557,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
unsigned long flags;
int i;
int bad = 0;
- int wasMlocked = TestClearPageMlocked(page);
+ int wasMlocked = __TestClearPageMlocked(page);
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 per_cpu_pages *pcp;
unsigned long flags;
- int wasMlocked = TestClearPageMlocked(page);
+ int wasMlocked = __TestClearPageMlocked(page);
kmemcheck_free_shadow(page, 0);