Re: [RFC PATCH 03/26] mm: make pageblock_order 2M per default

David Hildenbrand
2023-04-19T11:19:35Z

On 19.04.23 02:01, Kirill A. Shutemov wrote:
> On Tue, Apr 18, 2023 at 03:12:50PM -0400, Johannes Weiner wrote:
>> pageblock_order can be of various sizes, depending on configuration,
>> but the default is MAX_ORDER-1.
>
> Note that MAX_ORDER got redefined in -mm tree recently.
>
>> Given 4k pages, that comes out to
>> 4M. This is a large chunk for the allocator/reclaim/compaction to try
>> to keep grouped per migratetype. It's also unnecessary as the majority
>> of higher order allocations - THP and slab - are smaller than that.
>
> This seems way to x86-specific. Other arches have larger THP sizes. I
> believe 16M is common.
>

arm64 with 64k pages has ... 512 MiB IIRC :/ It's the weird one.

> Maybe define it as min(MAX_ORDER, PMD_ORDER)?

Sounds good to me.

--
Thanks,

David / dhildenb