Re: [RFC PATCH 12/15] mm: Make MAX_ORDER of buddy allocator configurable via Kconfig SET_MAX_ORDER.

[Vlastimil Babka]

On 8/5/21 9:02 PM, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>
> +config SET_MAX_ORDER
> +	int "Set maximum order of buddy allocator"
> +    depends on SPARSEMEM_VMEMMAP && (ARCH_FORCE_MAX_ORDER = 0)
> +	range 11 255
> +	default "11"
> +	help
> +	  The kernel memory allocator divides physically contiguous memory
> +	  blocks into "zones", where each zone is a power of two number of
> +	  pages.  This option selects the largest power of two that the kernel
> +	  keeps in the memory allocator.  If you need to allocate very large
> +	  blocks of physically contiguous memory, then you may need to
> +	  increase this value.
> +
> +	  This config option is actually maximum order plus one. For example,
> +	  a value of 11 means that the largest free memory block is 2^10 pages.

It's enough that it's confusing for the devs, we could spare the users and add
+1 to the value they specify :)

>  config HAVE_MEMBLOCK_PHYS_MAP
>  	bool
>  
>