I think the only distinction you need to make is memory where transactions make sense (user data), and where they don't (program state). I can see a scenario

I think the only distinction you need to make is memory where transactions make sense (user data), and where they don't (program state). I can see a scenario where opening a file for writing works just like mmap[0] with MAP_PRIVATE, i.e. you get blockwise copy-on-write, except everything will persist as if everything on your filesystem was under a VCS like git. I reckon just like volume management, encryption and snapshotting has steadily been folded in to the filesystem, so will the VFS and page cache. [0] http://man7.org/linux/man-pages/man2/mmap.2.html http://man7.org/linux/man-pages/man2/mmap.2.html