What is the GMP model?

Question

Accepted Answer

**GMP** — Goroutine (G), Machine (M), Processor (P).

**Components:**
- **G:** Goroutine.
- **M:** OS thread.
- **P:** Logical processor.

```go
fmt.Println("GOMAXPROCS:", runtime.GOMAXPROCS(0))
runtime.Gosched()
```

**Work stealing:**
- Steal from other P when queue empty.

**Handoff:**
- M in syscall → P given to another M.

**When to tune:**
- CPU-bound: GOMAXPROCS = NumCPU.
- Containers: adjust for cgroup.

**Common mistakes:**
- Not adjusting GOMAXPROCS in containers.
- Confusing `GOMAXPROCS(0)` with setting.
- Assuming goroutines always parallel.
- Using `LockOSThread()` without need.
- Not understanding work stealing.

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