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From: Christoph Lameter on 3 Aug 2010 23:00
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 2010-07-30 18:37:56.171016883 -0500
+++ linux-2.6/include/linux/mm_types.h 2010-07-30 18:45:28.624439565 -0500
@@ -40,10 +40,7 @@
* 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 2010-07-30 18:45:24.248349179 -0500
+++ linux-2.6/mm/slub.c 2010-07-30 18:45:28.628439648 -0500
@@ -144,7 +144,6 @@

#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 */
@@ -791,9 +790,6 @@
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);
@@ -2060,9 +2056,6 @@
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: [S+Q3 03/23] slub: Use a constant for a unspecified node.
Next: [S+Q3 22/23] slub: Cached object expiration