Re: [RFC] SL[AUO]B common code 3/9] Extract common fields from struct kmem_cache

Glauber Costa
2012-05-16T08:01:58Z

On 05/15/2012 12:15 AM, Christoph Lameter wrote:
> Define "COMMON" to include definitions for fields used in all
> slab allocators. After that it will be possible to share code that
> only operates on those fields of kmem_cache.
>
> The patch basically takes the slob definition of kmem cache and
> uses the field namees for the other allocators.
>
> The slob definition of kmem_cache is moved from slob.c to slob_def.h
> so that the location of the kmem_cache definition is the same for
> all allocators.
>
> Signed-off-by: Christoph Lameter<cl@linux.com>
>
> ---
> include/linux/slab.h | 11 +++++++++++
> include/linux/slab_def.h | 8 ++------
> include/linux/slub_def.h | 11 ++++-------
> mm/slab.c | 30 +++++++++++++++---------------
> mm/slob.c | 7 -------
> 5 files changed, 32 insertions(+), 35 deletions(-)
>
> Index: linux-2.6/include/linux/slab.h
> ===================================================================
> --- linux-2.6.orig/include/linux/slab.h 2012-05-11 08:34:30.272522792 -0500
> +++ linux-2.6/include/linux/slab.h 2012-05-11 09:36:35.292445608 -0500
> @@ -93,6 +93,17 @@
> (unsigned long)ZERO_SIZE_PTR)
>
> /*
> + * Common fields provided in kmem_cache by all slab allocators
> + */
> +#define SLAB_COMMON \
> + unsigned int size, align; \
> + unsigned long flags; \
> + const char *name; \
> + int refcount; \
> + void (*ctor)(void *); \
> + struct list_head list;
> +
> +/*
> * struct kmem_cache related prototypes

Isn't it better to define struct kmem_cache here, and then put the
non-common fields under proper ifdefs ?

I myself prefer that style, but style aside, we should aim for what you
call SLAB_COMMON to encompass as many fields as we can, so the others
will be kept to a minimum... It makes more sense, by looking from that
angle.

> Index: linux-2.6/mm/slob.c
> ===================================================================
> --- linux-2.6.orig/mm/slob.c 2012-05-11 08:34:31.792522763 -0500
> +++ linux-2.6/mm/slob.c 2012-05-11 09:42:52.032437799 -0500
> @@ -538,13 +538,6 @@ size_t ksize(const void *block)
> }
> EXPORT_SYMBOL(ksize);
>
> -struct kmem_cache {
> - unsigned int size, align;
> - unsigned long flags;
> - const char *name;
> - void (*ctor)(void *);
> -};
> -

Who defines struct kmem_cache for the slob now ?