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SubjectRe: [RFC] SLUB - define OO_ macro instead of hardcoded numbers
Cyrill Gorcunov wrote:
> 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);

Looks good to me. If Christoph ACKs this, please send me a proper patch
with your sign-off and I'll merge it to slab.git.

Pekka


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