I/O backends

I/O backends: how a task runtime waits for sockets.

Source: runtime/async/driver.pep

Backend

enum Backend

The I/O backend a runtime waits on sockets with (see RuntimeOptions.backend).

Cases

Automatic

Automatic

The best one the system has: epoll on Linux, kqueue on macOS, IOCP on Windows. The PEPPER_IO_BACKEND environment variable (epoll, io_uring, kqueue, iocp or poll) picks another.

Epoll

Epoll

Linux’s epoll, edge-triggered.

IoUring

IoUring

Linux’s io_uring (kernel 5.11 or later), waiting for sockets with one multishot poll request each. Not the default: container seccomp profiles and hardened kernels often refuse it.

Kqueue

Kqueue

The BSD and macOS kqueue, edge-triggered.

Iocp

Iocp

A Windows I/O completion port, fed readiness by AFD poll requests.

Poll

Poll

poll() (WSAPoll on Windows): available everywhere, but each wait passes every waiting socket to the system, so it suits few connections. The reference the others are tested against.