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From: Christoph Lameter on 9 Jul 2010 15:20
There is no need anymore for the "inuse" field in the page struct.
Extend the objects field to 32 bit allowing a practically unlimited
number of objects.

Signed-off-by: Christoph Lameter <cl(a)linux-foundation.org>

---
include/linux/mm_types.h | 5 +----
mm/slub.c | 7 -------
2 files changed, 1 insertion(+), 11 deletions(-)

Index: linux-2.6/include/linux/mm_types.h
===================================================================
--- linux-2.6.orig/include/linux/mm_types.h 2010-07-07 10:54:05.000000000 -0500
+++ linux-2.6/include/linux/mm_types.h 2010-07-07 10:54:36.000000000 -0500
@@ -40,10 +40,7 @@ struct page {
* to show when page is mapped
* & limit reverse map searches.
*/
- struct { /* SLUB */
- u16 inuse;
- u16 objects;
- };
+ u32 objects; /* SLUB */
};
union {
struct {
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2010-07-07 10:54:33.000000000 -0500
+++ linux-2.6/mm/slub.c 2010-07-07 10:54:36.000000000 -0500
@@ -145,7 +145,6 @@ 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 */

/* Internal SLUB flags */
#define __OBJECT_POISON 0x80000000UL /* Poison object */
@@ -768,9 +767,6 @@ static int verify_slab(struct kmem_cache
max_objects = ((void *)page->freelist - start) / s->size;
}

- if (max_objects > MAX_OBJS_PER_PAGE)
- max_objects = MAX_OBJS_PER_PAGE;
-
if (page->objects != max_objects) {
slab_err(s, page, "Wrong number of objects. Found %d but "
"should be %d", page->objects, max_objects);
@@ -1984,9 +1980,6 @@ static inline int slab_order(int size, i
int rem;
int min_order = slub_min_order;

- if ((PAGE_SIZE << min_order) / size > MAX_OBJS_PER_PAGE)
- return get_order(size * MAX_OBJS_PER_PAGE) - 1;
-
for (order = max(min_order,
fls(min_objects * size - 1) - PAGE_SHIFT);
order <= max_order; order++) {

--
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Prev: [PATCH, RT, RFC] Hacks allowing -rt to run on POWER7 / Powerpc.
Next: [S+Q2 13/19] slub: Extract hooks for memory checkers from hotpaths