On Mon, 12 Sep 2016 21:06:49 -0700 Dan Williams <dan.j.willi...@intel.com> wrote:
> 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. Yes, that's reasonable. Do you need page/block granularity? Do you need a way to advise/request the fs for a particular capability? Is it enough to request and check success? Would the capability be likely to change, and if so, how would you notify the app asynchronously?
