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Subject[slubllv3 07/21] slub: Do not use frozen page flag but a bit in the page counters
Do not use a page flag for the frozen bit. It needs to be part
of the state that is handled with cmpxchg_double(). So use a bit
in the counter struct in the page struct for that purpose.

Also all page start out as frozen pages so set the bit
when the page is allocated.

Signed-off-by: Christoph Lameter <cl@linux.com>


---
include/linux/mm_types.h | 5 +++--
include/linux/page-flags.h | 2 --
mm/slub.c | 12 ++++++------
3 files changed, 9 insertions(+), 10 deletions(-)
Index: linux-2.6/include/linux/mm_types.h
===================================================================
--- linux-2.6.orig/include/linux/mm_types.h 2011-04-15 12:54:32.000000000 -0500
+++ linux-2.6/include/linux/mm_types.h 2011-04-15 13:14:36.000000000 -0500
@@ -41,8 +41,9 @@ struct page {
* & limit reverse map searches.
*/
struct { /* SLUB */
- u16 inuse;
- u16 objects;
+ unsigned inuse:16;
+ unsigned objects:15;
+ unsigned frozen:1;
};
};
union {
Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h 2011-04-15 12:54:32.000000000 -0500
+++ linux-2.6/include/linux/page-flags.h 2011-04-15 13:14:36.000000000 -0500
@@ -212,8 +212,6 @@ PAGEFLAG(SwapBacked, swapbacked) __CLEAR

__PAGEFLAG(SlobFree, slob_free)

-__PAGEFLAG(SlubFrozen, slub_frozen)
-
/*
* Private page markings that may be used by the filesystem that owns the page
* for its own purposes.
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2011-04-15 13:11:25.000000000 -0500
+++ linux-2.6/mm/slub.c 2011-04-15 13:14:36.000000000 -0500
@@ -166,7 +166,7 @@ static inline int kmem_cache_debug(struc

#define OO_SHIFT 16
#define OO_MASK ((1 << OO_SHIFT) - 1)
-#define MAX_OBJS_PER_PAGE 65535 /* since page.objects is u16 */
+#define MAX_OBJS_PER_PAGE 32767 /* since page.objects is u15 */

/* Internal SLUB flags */
#define __OBJECT_POISON 0x80000000UL /* Poison object */
@@ -1013,7 +1013,7 @@ static noinline int free_debug_processin
}

/* Special debug activities for freeing objects */
- if (!PageSlubFrozen(page) && !page->freelist)
+ if (!page->frozen && !page->freelist)
remove_full(s, page);
if (s->flags & SLAB_STORE_USER)
set_track(s, object, TRACK_FREE, addr);
@@ -1402,7 +1402,7 @@ static inline int lock_and_freeze_slab(s
{
if (slab_trylock(page)) {
__remove_partial(n, page);
- __SetPageSlubFrozen(page);
+ page->frozen = 1;
return 1;
}
return 0;
@@ -1516,7 +1516,7 @@ static void unfreeze_slab(struct kmem_ca
{
struct kmem_cache_node *n = get_node(s, page_to_nid(page));

- __ClearPageSlubFrozen(page);
+ page->frozen = 0;
if (page->inuse) {

if (page->freelist) {
@@ -1867,7 +1867,7 @@ load_from_page:
flush_slab(s, c);

slab_lock(page);
- __SetPageSlubFrozen(page);
+ page->frozen = 1;

goto load_from_page;
}
@@ -2081,7 +2081,7 @@ static void __slab_free(struct kmem_cach
page->freelist = object;
page->inuse--;

- if (unlikely(PageSlubFrozen(page))) {
+ if (unlikely(page->frozen)) {
stat(s, FREE_FROZEN);
goto out_unlock;
}


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