Re: [LSF/MM/BPF TOPIC] 64k (or 16k) base page size on x86

[David Hildenbrand (Arm)]

On 7/19/26 23:24, Nadia Chambers wrote:
> Am Fr, Feb 20, 2026 um 11:24:37 +0100, David Hildenbrand (Arm) schrieb:
>> Right, see the proposal from Dev on the list.
>> From user-space POV, the pagesize would be 64K for these emulated processes.
>> That is, VMAs must be suitable aligned etc.
>> One key thing I think is that you could run such emulated-64k process (that
>> actually support it!) with 4k processes on the same machine, like Arm is
>> considering.
>> You would have no weird "vma crosses base pages" handling, which is just
>> rather nasty and makes my head hurt.
> 
> While it had to be written, it was a straightforward extension of
> converting ->vm_pgoff to being in MMUPAGE_SIZE (Kiryl's PTE_SIZE) units,
> recovering offsets into pages usw. Nothing seemed terribly hard to
> understand about it. Really, the code as it stands rarely approaches
> what it's doing in such a way that it broadly surveys the layout of vmas
> and pages and be conscious of whether pages spanned vmas or multiple
> vmas were representing maps of of fragments of pages, so I'm not
> convinced there's anything particularly unique to be afraid of here.

Just to be clear: I don't want this.

-- 
Cheers,

David