epoll is based on a "readiness" model (i.e. it tells when when you can start I/O). io_uring is based on a "completion" model (i.e. it tells you when I/O is fini

epoll is based on a "readiness" model (i.e. it tells when when you can start I/O). io_uring is based on a "completion" model (i.e. it tells you when I/O is finished). The latter is like Windows IOCP, where the C stands for Completion. Readiness models are rather useless for a local disk because, unlike with a socket, the disk is more or less always ready to receive a command.