Re: [SLUB 2/3] Large kmalloc pass through. Removal of large general slabs

Peter Zijlstra
2007-03-07T09:01:17Z

On Tue, 2007-03-06 at 18:35 -0800, Christoph Lameter wrote:
> Unlimited kmalloc size and removal of general caches >=4.
>
> We can directly use the page allocator for all allocations 4K and larger. This
> means that no general slabs are necessary and the size of the allocation passed
> to kmalloc() can be arbitrarily large. Remove the useless general caches over 4k.
>

> Index: linux-2.6.21-rc2-mm1/include/linux/slub_def.h
> ===================================================================
> --- linux-2.6.21-rc2-mm1.orig/include/linux/slub_def.h 2007-03-06 17:56:14.000000000 -0800
> +++ linux-2.6.21-rc2-mm1/include/linux/slub_def.h 2007-03-06 17:57:11.000000000 -0800
> @@ -55,7 +55,7 @@ struct kmem_cache {
> */
> #define KMALLOC_SHIFT_LOW 3
>
> -#define KMALLOC_SHIFT_HIGH 18
> +#define KMALLOC_SHIFT_HIGH 11
>
> #if L1_CACHE_BYTES <= 64
> #define KMALLOC_EXTRAS 2
> @@ -93,13 +93,6 @@ static inline int kmalloc_index(int size
> if (size <= 512) return 9;
> if (size <= 1024) return 10;
> if (size <= 2048) return 11;
> - if (size <= 4096) return 12;
> - if (size <= 8 * 1024) return 13;
> - if (size <= 16 * 1024) return 14;
> - if (size <= 32 * 1024) return 15;
> - if (size <= 64 * 1024) return 16;
> - if (size <= 128 * 1024) return 17;
> - if (size <= 256 * 1024) return 18;
> return -1;
> }

Perhaps so something with PAGE_SIZE here, as you know there are
platforms/configs where PAGE_SIZE != 4k :-)