On Mon, Sep 12, 2016 at 6:31 PM, Nicholas Piggin <npig...@gmail.com> wrote: > On Mon, 12 Sep 2016 08:01:48 -0700 [..] > That said, a noop system call is on the order of 100 cycles nowadays, > so rushing to implement these APIs without seeing good numbers and > actual users ready to go seems premature. *This* is the real reason > not to implement new APIs yet.
Yes, and harvesting the current crop of low hanging performance fruit in the filesystem-DAX I/O path remains on the todo list. In the meantime we're pursuing this mm api, mincore+ or whatever we end up with, to allow userspace to distinguish memory address ranges that are backed by a filesystem requiring coordination of metadata updates + flushes for updates, vs something like device-dax that does not.
