On Thu, Aug 10, 2023 at 04:57:11PM -0400, Peter Xu wrote: > AFAICS if that patch was all correct (while I'm not yet sure..), you can > actually fit your new total mapcount field into page 1 so even avoid the > extra cacheline access. You can have a look: the trick is refcount for > tail page 1 is still seems to be free on 32 bits (if that was your worry > before). Then it'll be very nice if to keep Hugh's counter all in tail 1. No, refcount must be 0 on all tail pages. We rely on this in many places in the MM.
