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SubjectRe: [RFC PATCH] mm/zsmalloc: remove unnecessary check
On Thu, Nov 20, 2014 at 09:21:56PM +0800, Mahendran Ganesh wrote:
> ZS_SIZE_CLASSES is calc by:
> ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1)
>
> So when i is in [0, ZS_SIZE_CLASSES - 1), the size:
> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA
> will not be greater than ZS_MAX_ALLOC_SIZE
>
> This patch removes the unnecessary check.

It depends on ZS_MIN_ALLOC_SIZE.
For example, we would change min to 8 but MAX is still 4096.
ZS_SIZE_CLASSES is (4096 - 8) / 16 + 1 = 256 so 8 + 255 * 16 = 4088,
which exceeds the max.

>
> Signed-off-by: Mahendran Ganesh <opensource.ganesh@gmail.com>
> ---
> mm/zsmalloc.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b3b57ef..f2279e2 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -973,8 +973,6 @@ struct zs_pool *zs_create_pool(gfp_t flags)
> struct size_class *prev_class;
>
> size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
> - if (size > ZS_MAX_ALLOC_SIZE)
> - size = ZS_MAX_ALLOC_SIZE;
> pages_per_zspage = get_pages_per_zspage(size);
>
> /*
> --
> 1.7.9.5
>
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--
Kind regards,
Minchan Kim


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