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

[Anshuman Khandual]

On 2/5/21 1:50 PM, David Hildenbrand wrote:
> 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?

Correct. MAX_ORDER gets incremented when THP is enabled.

config FORCE_MAX_ZONEORDER
        int
        default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE)
        default "12" if (ARM64_16K_PAGES && TRANSPARENT_HUGEPAGE)
        default "11"