Re: [PATCHv3 1/5] lib/genalloc.c: Add power aligned algorithm

Will Deacon
2014-06-20T09:34:15Z

Hi Laura,

On Tue, Jun 17, 2014 at 02:39:21AM +0100, Laura Abbott wrote:
> One of the more common algorithms used for allocation
> is to align the start address of the allocation to
> the order of size requested. Add this as an algorithm
> option for genalloc.

Good idea, I didn't know this even existed!

> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
> ---
> include/linux/genalloc.h | 4 ++++
> lib/genalloc.c | 21 +++++++++++++++++++++
> 2 files changed, 25 insertions(+)
>
> diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h
> index 1c2fdaa..3cd0934 100644
> --- a/include/linux/genalloc.h
> +++ b/include/linux/genalloc.h
> @@ -110,6 +110,10 @@ extern void gen_pool_set_algo(struct gen_pool *pool, genpool_algo_t algo,
> extern unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
> unsigned long start, unsigned int nr, void *data);
>
> +extern unsigned long gen_pool_first_fit_order_align(unsigned long *map,
> + unsigned long size, unsigned long start, unsigned int nr,
> + void *data);
> +
> extern unsigned long gen_pool_best_fit(unsigned long *map, unsigned long size,
> unsigned long start, unsigned int nr, void *data);
>
> diff --git a/lib/genalloc.c b/lib/genalloc.c
> index bdb9a45..9758529 100644
> --- a/lib/genalloc.c
> +++ b/lib/genalloc.c
> @@ -481,6 +481,27 @@ unsigned long gen_pool_first_fit(unsigned long *map, unsigned long size,
> EXPORT_SYMBOL(gen_pool_first_fit);
>
> /**
> + * gen_pool_first_fit_order_align - find the first available region
> + * of memory matching the size requirement. The region will be aligned
> + * to the order of the size specified.
> + * @map: The address to base the search on
> + * @size: The bitmap size in bits
> + * @start: The bitnumber to start searching at
> + * @nr: The number of zeroed bits we're looking for
> + * @data: additional data - unused

It doesn't look unused to me.

> + */
> +unsigned long gen_pool_first_fit_order_align(unsigned long *map,
> + unsigned long size, unsigned long start,
> + unsigned int nr, void *data)
> +{
> + unsigned long order = (unsigned long) data;
> + unsigned long align_mask = (1 << get_order(nr << order)) - 1;

Why isn't the order just order?

Will