Overview and classification of supported io_uring async operation variants.

io_uring supports a wide range of asynchronous operations and provides many advanced features, resulting in a rich variety of async operation types. Condy offers a detailed and structured classification of io_uring's async operations. This documentation records these categories, which not only help Condy users understand the interfaces, but also provide io_uring users with a basic overview.

Note: This document is written from the perspective of Condy; some liburing interfaces may not be included.

Basic Operations

These are fundamental asynchronous operations. Many of them are asynchronous versions of existing system calls. Each operation is submitted once and returns once.

Multishot Operations

These asynchronous operations are submitted once but may return results multiple times.

Zero Copy Tx Operations

These asynchronous operations, when successful, return twice: the first return indicates the operation is complete, and the second indicates the buffer is no longer needed.

Fixed Fd Operations

These asynchronous operations accept the index of a file registered with the kernel, rather than a file descriptor.

Direct Operations

These asynchronous operations, unlike their original counterparts which return a file descriptor, instead register the file with the kernel and return the index of the file in the kernel's registered file table.

Fixed Buffer Operations

These asynchronous operations additionally accept the index of a memory region registered with the kernel.

Provided Buffer Operations

These asynchronous operations accept a set of pre-provided buffers, rather than a specific single buffer. During the async operation, one or more buffers from the provided set are selected for reading or writing.