GP's question is perfectly valid. It doesn't have to be called within a tight loop at all. It could be a latency sensitive routine for example. I can see at least a few real life applications where it would make sense to have the syscall vDSO'd.
It’s not a VDSO because it was never added as one. “Not a VDSO” is the default, a VDSO is additional complexity and maintenance so you need to justify its addition / existence, not its non-existence.
I think we're just talking past each other. I'm asking why you'd want to vDSO getuid(), not getpid(). I can imagine cases where you'd repeatedly be calling getpid().
Eh. All of these things requiring a context switch seems alien to me. So it’s less of a use case and more “just make it fast” since the incremental cost should be 0?
