Re: kmem_cache_create loop for find the proper gfporder

[Pekka Enberg]

On 3/25/07, Bin Chen <binary.chen@xxxxxxxxx> wrote:
> It is done by increase gfporder for low number to high(possibly 0 to
> MAX_GFP_ORDER). But why increase the gfporder(or slab size) can
> decrease the internal fragmentation?)
>
> A simple example, suppose the slab management stuff is kept off-slab,
> if the gfporder is zero, and the object size in slab is 1000, the
> wasted space is 4096 mod 1000 = 96, but with 4096 * 2(increase
> gfporder by 1), the space is 8192 mod 1000 = 192, 192 > 96.

You didn't simulate the algorithm long enough. If you had, you'd hit
order five which wastes only 72 bytes in your example.

                                Pekka
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