----- Ursprüngliche Mail ----- > Von: "David Hildenbrand" <david@xxxxxxxxxx> > But why is that required? What is the target use case? (I did not get > the cover letter in my inbox) > > We're running slowly but steadily out of bits, so we better make wise > decisions. > > Also, consider: Architectures where the dirty/access bit is not HW > managed could indicate "writable" here although we *will* get a page > fault to set the page dirty/accessed. I'm currently investigating why a real-time application faces unexpected page faults. Page faults are usually fatal for real-time work loads because the latency constraints are no longer met. So, I wrote a small tool to inspect the memory mappings of a process to find areas which are not correctly pre-faulted. While doing so I noticed that there is currently no way to detect CoW mappings. Exposing the writable property of a PTE seemed like a good start to me. > So best this can universally do is say "this PTE currently has write > permissions". Ok. Thanks, //richard
