10ns latency means that a file entry/inode/block is available just 10-30 CPU cycles after it is requested. Suddenly the 1000 CPU cycles spent dispatching the system call look very inefficient by comparison.

Obsolete might not be the right term, but there is essentially no way that open/read/write can take proper advantage of this kind of low latency storage. We are going to need a new way to abstract and interface with this persistent storage.

Read/write are certainly a bit slow, but this may well be acceptable for most applications. High performance apps can use mmap, which can be extended to directly map the nonvolatile memory in question.

Or a way to make system calls faster, some sort of vdso with the ability to switch privilege level.

That's how __vsyscall works now.

__vsyscall simply abstracts away the actual system call invocation strategy (int, sysenter, syscall), but doesn't change the model at all.

Anyway, what I was thinking was similar to call gates, which were phased out for being slow. Probably just making syscall faster in the CPU and reducing the overhead kernel side would be enough.