[VMIL'25] The Wild West of post-POSIX IO Interfaces

Anil Madhavapeddy traces the evolution of asynchronous and shared-memory I/O mechanisms like io_uring and libdispatch beyond the POSIX model.

The Wild West of post-POSIX IO Interfaces (Video, VMIL 2025) Anil Madhavapeddy (University of Cambridge, UK) Abstract: The POSIX programming model has provided a long-standing abstraction for I/O, but contemporary systems increasingly expose interfaces that deviate from this model in pursuit of performance, scalability, and flexibility. This talk traces the evolution of shared-memory and asynchronous I/O mechanisms, beginning with early hypervisor-driven approaches such as Xen’s virtual device drivers, and continuing through to modern system interfaces including Linux’s io_uring and macOS’s libdispatch. These developments illustrate the growing fragmentation of the I/O landscape, but also highlight opportunities for unifying abstractions that balance expressivity with ergonomics for these highly concurrent interfaces. As a case study, I will discuss how Docker integrates these heterogeneous interfaces into end-to-end data paths. Finally, I will present ongoing work in the OCaml 5 ecosystem, where effect-based concurrency abstractions, as implemented in the Eio library, offer a principled way of reconciling post-POSIX I/O mechanisms with high-level language runtimes. My perspective aims to inform discussions on virtual machine and runtime design, with implications for concurrency models, performance engineering, and cross-platform systems support. Presentation at the VMIL 2025 workshop, Oct 15, 2025, conf.researchr.org/home/icfp-splash-2025/vmil-2025 Sponsored by ACM SIGPLAN.