On Thu, Jun 09, 2022 at 10:41:22AM +0800, tjytimi wrote:
> The worst case is that the new memory range overlaps all existing
> regions,which need type->cnt + 1 free area of struct memblock_region.
> So if type->cnt + 1 + type->cnt is less than type->max,we can insert
> regions directly.And becase of merge operation in the end of function,
> tpye->cnt increase slowly for many cases.So this patch can avoid
> unnecessary repeat for many cases when add new memory range.
>
> Signed-off-by: tjytimi <tjytimi@xxxxxxx>
> ---
> mm/memblock.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e4f03a6e8..243cd7de5 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -602,6 +602,9 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
> base = obase;
> nr_new = 0;
>
> + if (type->cnt<<1 < type->max - 1)
> + insert = true;
> +
Several things here:
- cnt * 2 looks clearer than cnt << 1 and the performance difference (if
any) is negligible
- I think checking that cnt + 1 < max is easier to read
- there should be space around operators, i.e. cnt << 1
I'd also appreciate a comment in the code with the explanation similar
to the changelog
> for_each_memblock_type(idx, type, rgn) {
> phys_addr_t rbase = rgn->base;
> phys_addr_t rend = rbase + rgn->size;
> --
> 2.32.0
>
--
Sincerely yours,
Mike.
