For me it's less about performance than cleaner concurrency. Do you know (unless this has been fixed recently) that io_uring is the only way you can asynchronously open a file? Erlang and GHC both have lightweight threads/processes that use asynchronous i/o (for sockets, say), but they keep a separate OS threadpool to be able to do stuff like open files. io_uring lets you write an actual multitasking OS-like thing that runs in a single Linux thread.