Re: [Patch v2 4/8] mm/memblock: remove consecutive regions at once

[Mike Rapoport <rppt@kernel.org>]

On Thu, Apr 25, 2024 at 07:19:25AM +0000, Wei Yang wrote:
> In memblock_remove_range, we would remove consecutive regions after
> isolation.
> 
> Instead of removing each region from end to start one by one, we could
> remove those consecutive regions at once.

I don't think this is worth the churn.
 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> ---
>  mm/memblock.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 5a363ef283d0..53e3aa2cd9a2 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -343,12 +343,15 @@ static phys_addr_t __init_memblock memblock_find_in_range(phys_addr_t start,
>  	return ret;
>  }
>  
> -static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
> +static void __init_memblock memblock_remove_regions(struct memblock_type *type,
> +						    unsigned long r,
> +						    unsigned int num)
>  {
> -	type->total_size -= type->regions[r].size;
> -	memmove(&type->regions[r], &type->regions[r + 1],
> -		(type->cnt - (r + 1)) * sizeof(type->regions[r]));
> -	type->cnt--;
> +	for (int i = 0; i < num; i++)
> +		type->total_size -= type->regions[r + i].size;
> +	memmove(&type->regions[r], &type->regions[r + num],
> +		(type->cnt - (r + num)) * sizeof(type->regions[r]));
> +	type->cnt -= num;
>  
>  	/* Special case for empty arrays */
>  	if (type->cnt == 0) {
> @@ -360,6 +363,11 @@ static void __init_memblock memblock_remove_region(struct memblock_type *type, u
>  	}
>  }
>  
> +static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r)
> +{
> +	memblock_remove_regions(type, r, 1);
> +}
> +
>  #ifndef CONFIG_ARCH_KEEP_MEMBLOCK
>  /**
>   * memblock_discard - discard memory and reserved arrays if they were allocated
> @@ -846,14 +854,14 @@ static int __init_memblock memblock_remove_range(struct memblock_type *type,
>  					  phys_addr_t base, phys_addr_t size)
>  {
>  	int start_rgn, end_rgn;
> -	int i, ret;
> +	int ret;
>  
>  	ret = memblock_isolate_range(type, base, size, &start_rgn, &end_rgn);
>  	if (ret)
>  		return ret;
>  
> -	for (i = end_rgn - 1; i >= start_rgn; i--)
> -		memblock_remove_region(type, i);
> +	if (end_rgn - start_rgn)
> +		memblock_remove_regions(type, start_rgn, end_rgn - start_rgn);
>  	return 0;
>  }
>  
> -- 
> 2.34.1
> 

-- 
Sincerely yours,
Mike.