Likely, we just want to read "the real deal" on both sides of the pte_same()
handling.
Sorry I'm not sure I understand? You mean read the full pte including
access/dirty? That's the same as dropping the patch, right? Of course if we do
that, we still have to keep pte_get_lockless() around for this case. In an ideal
world we would convert everything over to ptep_get_lockless_norecency() and
delete ptep_get_lockless() to remove the ugliness from arm64.
Yes, agreed. Patch #3 does not look too crazy and it wouldn't really affect any
architecture.
I do wonder if pte_same_norecency() should be defined per architecture and the
default would be pte_same(). So we could avoid the mkold etc on all other
architectures.
Wouldn't that break it's semantics? The "norecency" of
ptep_get_lockless_norecency() means "recency information in the returned pte may
be incorrect". But the "norecency" of pte_same_norecency() means "ignore the
access and dirty bits when you do the comparison".
I think you could only do the optimization you describe if you required that
pte_same_norecency() would only be given values returned by
ptep_get_lockless_norecency() (or ptep_get_norecency()). Even then, its not
quite the same; if a page is accessed between gets one will return true and the
other false.