Hello, Axel,
On Wed, Sep 22, 2021 at 10:04:03AM -0700, Axel Rasmussen wrote:
> Thanks for discussing the design Peter. I have some ideas which might
> make for a nicer v2; I'll massage the code a bit and see what I can
> come up with.
Sure thing. Note again that as I don't have a strong opinion on that, feel
free to keep it. However if you provide v2, I'll read.
[off-topic below]
Another thing I probably have forgot but need your confirmation is, when you
worked on uffd minor mode, did you explicitly disable thp, or is it allowed?
When I'm reworking the uffd-wp series, I noticed that commit e1e267c7928f
("khugepaged: skip collapse if uffd-wp detected", 2020-04-07) was actually
awkward and not efficient, as we can simply lookup the vma flags for detecting
uffd-wp enablement. I'm preparing a patch for it to do it by checking vmas
(and that patch will also pave the way for file-backed).
Then I noticed we need similar thing for minor mode?
I think the answer is yes, but I didn't see any code that explicitly handled
thp for minor mode, do you remember?
To be explicit, what if in mcontinue_atomic_pte() we get a shmem_getpage() call
with a thp returned? Will minor mode break?
I plan to post the khugepaged patch soon and I plan to cover minor mode too
there, but I'm not sure whether that's enough, as the thp can be there from the
1st day I think, but I could have missed something.
--
Peter Xu
