My thinking was, that if you have a large VMA, with ordinary pagemap you have to copy 8byte per entry (and have room for that somewhere in user space). In theory, with the scanning feature, you can leave that ... scanning to the kernel and don't have to do any copying/allocate space for it in user space etc.
That makes perfect sense!
I think this one will go a little lower on priorities + I'll come back to it but I"ll put it on the one reliable todo list I have, the whiteboard in my home office :) everything on that list at least eventually gets looked at, majority get done.
Sounds good. I'm sure Android folks will speak up in case they require more efficient scanning.
-- Cheers,
David / dhildenb
Great minds think alike though ;) as soon as I saw this I did think about extending it, but seems I mistakenly dismissed for uffd reasons.
We should probably look into cleaning up + improving the documentation around the pagemap scan feature at some point. Well, something for another day :)