High-performance I/O using io_uring via osmo_io (osmodevcon2024)

Traditional socket I/O via `read/write/recvfrom/sendto/recvmsg/sendmsg` and friends creates a very high system call load. A highly-loaded osmo-bsc spends most of its time in syscall entry and syscall exit. `io_uring` is a modern Linux kernel mechanism to avoid this syscall overhead. We have introduced the `osmo_io`API to libosmocore as a generic back-end for non-blocking/asynchronous I/O and a back-end for our classic `osmo_fd` / `poll` approach as well as a new backend for `io_uring`. The talk will cover * a very basic io_uring introduction * a description of the osmo_io API * the difficulties porting from osmo_fd to osmo_io * status of porting various sub-systems over to osmo_io about this event: https://pretalx.sysmocom.de/osmodevcon2024/talk/ZBJWUP/