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Linux AIO for Network I/O

1 post · Jan 2019

What this trail covers

Cloudflare is exploring and implementing the Linux AIO API for network I/O operations, moving beyond its traditional use for disk I/O. This involves understanding and leveraging `io_submit` for syscall batching and optimizing event retrieval by directly accessing the kernel's ring buffer, bypassing the `io_getevents` syscall for improved performance in high-concurrency network servers. The company is investigating the tracepoints and kernel mechanisms involved in worker creation and management to optimize its use of io_uring.

All Cloudflare trails
  1. io_submit: The epoll alternative you've never heard aboutThis post details how the Linux AIO API, traditionally used for disk I/O, can be leveraged for network sockets. It explains the core Linux AIO syscalls (`io_setup`, `io_submit`, `io_getevents`) and demonstrates their use with a simple file read example. Crucially, it highlights that for network sockets, `io_submit` performs the actual work, similar to blocking `read()` calls, but enables syscall batching. The post further optimizes performance by showing how to bypass the `io_getevents` syscall by directly accessing the kernel's ring buffer for completion events, significantly reducing overhead for high-concurrency network servers.