Re: [PATCH v2 00/19] mm: Support huge pfnmaps

[Peter Xu]

On Mon, Sep 09, 2024 at 04:03:55AM +0000, Ankit Agrawal wrote:
> > More architectures / More page sizes
> > ------------------------------------
> > 
> > Currently only x86_64 (2M+1G) and arm64 (2M) are supported.  There seems to
> > have plan to support arm64 1G later on top of this series [2].
> > 
> > Any arch will need to first support THP / THP_1G, then provide a special
> > bit in pmds/puds to support huge pfnmaps.
> 
> Just to confirm, would this also not support 512M for 64K pages on aarch64
> with special PMD? Or am I missing something?

I don't think it's properly tested yet, but logically it should be
supported indeed, as here what matters is "pmd/pud", not the explicit size
that it uses.

> 
> > remap_pfn_range() support
> > -------------------------
> > 
> > Currently, remap_pfn_range() still only maps PTEs.  With the new option,
> > remap_pfn_range() can logically start to inject either PMDs or PUDs when
> > the alignment requirements match on the VAs.
> >
> > When the support is there, it should be able to silently benefit all
> > drivers that is using remap_pfn_range() in its mmap() handler on better TLB
> > hit rate and overall faster MMIO accesses similar to processor on hugepages.
> 
> Does Peter or other folks know of an ongoing effort/patches to extend
> remap_pfn_range() to use this?

Not away of any from my side.

Thanks,

-- 
Peter Xu