Re: [PATCH v11 00/25] mm/gup: track dma-pinned pages: FOLL_PIN

[John Hubbard]

On 12/20/19 4:33 PM, Dan Williams wrote:
...
>> I believe there might be also a different solution for this: For
>> transparent huge pages, we could find a space in 'struct page' of the
>> second page in the huge page for proper pin counter and just account pins
>> there so we'd have full width of 32-bits for it.
> 
> That would require THP accounting for dax pages. It is something that
> was probably going to be needed, but this would seem to force the
> issue.
> 

Thanks for mentioning that, it wasn't obvious to me yet. 

How easy is it for mere mortals outside of Intel, to set up a DAX (nvdimm?)
test setup? I'd hate to go into this without having that coverage up
and running. It's been sketchy enough as it is. :)

thanks,
-- 
John Hubbard
NVIDIA