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SubjectRe: [RFC] SLUB - define OO_ macro instead of hardcoded numbers
[Pekka Enberg - Wed, Oct 22, 2008 at 08:50:56PM +0300]
> Christoph Lameter wrote:
>> On Wed, 22 Oct 2008, Cyrill Gorcunov wrote:
>>
>>> Christoph how about this one?
>>
>> Ok. Looks a bit better but we still have two maxes here
>>
>> s->max which refers to the maximum number of objects per slab page for
>> a specific slab cache (depends on the runtime configuration).
>> OO_MAX_OBJS refers to the maximum number of objects per slab page that
>> any slab cache can be configured for which is a compile time limit.
>>
>> Maybe this is okay, Pekka?
>
> Maybe call the page->objects maximum MAX_OBJS_PER_PAGE as it's not
> strictly related to the other OO code?
>
> Pekka
>

Something like that?

- Cyrill -
---
mm/slub.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
Index: linux-2.6.git/mm/slub.c
===================================================================
--- linux-2.6.git.orig/mm/slub.c 2008-10-22 21:11:26.000000000 +0400
+++ linux-2.6.git/mm/slub.c 2008-10-22 21:57:11.000000000 +0400
@@ -153,6 +153,10 @@
#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
#endif

+#define OO_SHIFT 16
+#define OO_MASK ((1 << OO_SHIFT) - 1)
+#define MAX_OBJS_PER_PAGE 65535 /* see struct page.objects */
+
/* Internal SLUB flags */
#define __OBJECT_POISON 0x80000000 /* Poison object */
#define __SYSFS_ADD_DEFERRED 0x40000000 /* Not yet visible via sysfs */
@@ -290,7 +294,7 @@ static inline struct kmem_cache_order_ob
unsigned long size)
{
struct kmem_cache_order_objects x = {
- (order << 16) + (PAGE_SIZE << order) / size
+ (order << OO_SHIFT) + (PAGE_SIZE << order) / size
};

return x;
@@ -298,12 +302,12 @@ static inline struct kmem_cache_order_ob

static inline int oo_order(struct kmem_cache_order_objects x)
{
- return x.x >> 16;
+ return x.x >> OO_SHIFT;
}

static inline int oo_objects(struct kmem_cache_order_objects x)
{
- return x.x & ((1 << 16) - 1);
+ return x.x & OO_MASK;
}

#ifdef CONFIG_SLUB_DEBUG
@@ -764,8 +768,8 @@ static int on_freelist(struct kmem_cache
}

max_objects = (PAGE_SIZE << compound_order(page)) / s->size;
- if (max_objects > 65535)
- max_objects = 65535;
+ 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 "
@@ -1819,8 +1823,8 @@ static inline int slab_order(int size, i
int rem;
int min_order = slub_min_order;

- if ((PAGE_SIZE << min_order) / size > 65535)
- return get_order(size * 65535) - 1;
+ 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);

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