On 12.01.23 22:33, Peter Xu wrote:
On Thu, Jan 12, 2023 at 04:17:52PM -0500, James Houghton wrote:
I'll look into it, but doing it this way will use _mapcount, so we
won't be able to use the vmemmap optimization. I think even if we do
use Hugh's approach, refcount is still being kept on the head page, so
there's still an overflow risk there (but maybe I am
misunderstanding).
Could you remind me what's the issue if using refcount on the small pages
rather than the head (assuming vmemmap still can be disabled)?
The THP-way of doing things is refcounting on the head page. All folios
use a single refcount on the head.
There has to be a pretty good reason to do it differently.
--
Thanks,
David / dhildenb
