io_uring 이란?
- Submission queue (SQ): A user space process uses the submission queue to send asynchronous I/O requests to the kernel.
- Completion queue (CQ): The kernel uses the completion queue to send the results of asynchronous I/O operations back to user space.

SQPOLL을 이용한 submit syscall까지 생략...
IORING_OP_RECV_ZC라는 엄청난 기술을 공부해보자 한다.