Defines how many entries can submission queue hold.
SetupParameters
io_uring_setup(2) returns a new file descriptor on success. The application may then provide the file descriptor in a subsequent mmap(2) call to map the submission and completion queues, or to the io_uring_register(2) or io_uring_enter(2) system calls.
On error, -1 is returned and errno is set appropriately.
io_uring_setup(2)
Setup a context for performing asynchronous I/O.
The io_uring_setup() system call sets up a submission queue (SQ) and completion queue (CQ) with at least entries entries, and returns a file descriptor which can be used to perform subsequent operations on the io_uring instance. The submission and completion queues are shared between userspace and the kernel, which eliminates the need to copy data when initiating and completing I/O.