Re: [RFC 2/3] arm64/hugetlb: Enable HUGETLB_PAGE_SIZE_VARIABLE

[David Hildenbrand]

On 04.02.21 08:01, Anshuman Khandual wrote:
> MAX_ORDER which invariably depends on FORCE_MAX_ZONEORDER can be a variable
> for a given page size, depending on whether TRANSPARENT_HUGEPAGE is enabled
> or not. In certain page size and THP combinations HUGETLB_PAGE_ORDER can be
> greater than MAX_ORDER, making it unusable as pageblock_order.

Just so I understand correctly, this does not imply that we have THP 
that exceed the pageblock size / MAX_ORDER size, correct?


> This enables HUGETLB_PAGE_SIZE_VARIABLE making pageblock_order a variable
> rather than the compile time constant HUGETLB_PAGE_ORDER which could break
> MAX_ORDER rule for certain configurations.
>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>   arch/arm64/Kconfig | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 175914f2f340..c4acf8230f20 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1918,6 +1918,10 @@ config ARCH_ENABLE_THP_MIGRATION
>   	def_bool y
>   	depends on TRANSPARENT_HUGEPAGE
>   
> +config HUGETLB_PAGE_SIZE_VARIABLE
> +	def_bool y
> +	depends on HUGETLB_PAGE
> +
>   menu "Power management options"
>   
>   source "kernel/power/Kconfig"


--
Thanks,

David / dhildenb