goroutines

goroutines is experimental. It landed after 0.5.1, so import goroutines is not available in that release.

Go-style goroutine runtime for V, implementing the GMP (Goroutine-Machine-Processor) scheduling model translated from the Go runtime (src/runtime/proc.go, runtime2.go, chan.go).

Overview

This module provides lightweight goroutines for V's go keyword, as opposed to spawn which creates OS threads.

GMP Model

G (Goroutine): Lightweight unit of execution with its own stack (~8KB default)
M (Machine): OS thread that executes goroutines
P (Processor): Logical processor with a local run queue (one per CPU core)

Key Features

Work stealing: Idle processors steal work from busy ones
Local run queues: Lock-free per-P queues minimize contention
Global run queue: Overflow and fairness mechanism
Goroutine parking: Efficient blocking/unblocking for channels
G reuse: Dead goroutines are recycled to reduce allocation

Usage

// `go` launches a goroutine (lightweight, scheduled by GMP)
go expensive_computation()

// `spawn` launches an OS thread (traditional V behavior)
spawn blocking_io_task()

Architecture

Translated from Go's runtime source:

| Go Source | V Module File | Purpose | |-----------|---------------|---------| | runtime2.go | goroutines.v | Core data structures (G, M, P, Sched) | | proc.go | scheduler.v | Scheduler loop, work stealing, run queues | | proc.go | park.v | gopark/goready, Sudog, WaitQ | | proc.go | init.v | Initialization (schedinit, procresize) | | chan.go | chan.v | Channel implementation | | asm (gogo/gosave) | context_nix.c.v | Context switching (ucontext) | | asm (gogo/gosave) | context_windows.c.v | Context switching (Windows fibers) |