Re: [RFC PATCH 00/15] Make MAX_ORDER adjustable as a kernel boot time parameter.

[Hugh Dickins]

On Fri, 6 Aug 2021, Zi Yan wrote:
> 
> In addition, I would like to share more detail on my plan on supporting 1GB PUD THP.
> This patchset is the first step, enabling kernel to allocate 1GB pages, so that
> user can get 1GB THPs from ZONE_NORMAL and ZONE_MOVABLE without using
> alloc_contig_pages() or CMA allocator. The next step is to improve kernel memory
> fragmentation handling for pages up to MAX_ORDER, since currently pageblock size
> is still limited by memory section size. As a result, I will explore solutions
> like having additional larger pageblocks (up to MAX_ORDER) to counter memory
> fragmentation. I will discover what else needs to be solved as I gradually improve
> 1GB PUD THP support.

Sorry to be blunt, but let me state my opinion: 2MB THPs have given and
continue to give us more than enough trouble.  Complicating the kernel's
mm further, just to allow 1GB THPs, seems a very bad tradeoff to me.  I
understand that it's an appealing personal project; but for the sake of
of all the rest of us, please leave 1GB huge pages to hugetlbfs (until
the day when we are all using 2MB base pages).

Hugh