《Go 语言运行时原理》2.1 G/M/P 结构与状态机

package main

import (
	"runtime"
	"sync"
	"time"
)

//go:noinline
func burn(n int) uint64 {
	var x uint64 = 1
	for i := 0; i < n; i++ {
		x = x*1664525 + 1013904223
	}
	return x
}

func main() {
	var wg sync.WaitGroup
	var sum [24]uint64
	for w := 0; w < 24; w++ {
		wg.Add(1)
		go func(id int) {
			defer wg.Done()
			deadline := time.Now().Add(2500 * time.Millisecond)
			for time.Now().Before(deadline) {
				sum[id] = burn(50000)
			}
		}(w)
	}
	wg.Wait()
	runtime.KeepAlive(sum)
}

GODEBUG=schedtrace=1500,scheddetail=1 ./sched

SCHED 0ms: gomaxprocs=10 idleprocs=7 threads=4 spinningthreads=1 needspinning=0 idlethreads=1 runqueue=0 gcwaiting=false nmidlelocked=-1 stopwait=0 sysmonwait=false
  P8: status=1 schedtick=0 syscalltick=0 m=3 runqsize=0 gfreecnt=0 timerslen=0
  P9: status=0 schedtick=2 syscalltick=0 m=nil runqsize=0 gfreecnt=0 timerslen=0
  M3: p=8 curg=nil mallocing=0 throwing=0 preemptoff= locks=17 dying=0 spinning=false blocked=false lockedg=nil
  M2: p=nil curg=nil mallocing=0 throwing=0 preemptoff= locks=0 dying=0 spinning=false blocked=true lockedg=nil
  M1: p=nil curg=nil mallocing=0 throwing=0 preemptoff= locks=32 dying=0 spinning=false blocked=false lockedg=nil
  M0: p=nil curg=nil mallocing=0 throwing=0 preemptoff= locks=17 dying=0 spinning=false blocked=false lockedg=1
  G1: status=1(chan receive) m=nil lockedm=0
  G2: status=4(force gc (idle)) m=nil lockedm=nil
  G3: status=4(GC sweep wait) m=nil lockedm=nil
  G4: status=1() m=nil lockedm=nil

SCHED 1511ms: gomaxprocs=10 idleprocs=0 threads=11 spinningthreads=0 needspinning=1 idlethreads=0 runqueue=10 gcwaiting=false nmidlelocked=0 stopwait=0 sysmonwait=false
  P0: status=1 schedtick=47 syscalltick=0 m=4 runqsize=0 gfreecnt=0 timerslen=0
  P1: status=1 schedtick=46 syscalltick=0 m=10 runqsize=1 gfreecnt=0 timerslen=0
  G1: status=4(sync.WaitGroup.Wait) m=nil lockedm=nil
  G2: status=4(force gc (idle)) m=nil lockedm=nil
  G17: status=4(GOMAXPROCS updater (idle)) m=nil lockedm=nil
  G18: status=1() m=nil lockedm=nil
  G23: status=2() m=8 lockedm=nil
  G28: status=2() m=10 lockedm=nil
  G34: status=2() m=6 lockedm=nil
  G37: status=2() m=9 lockedm=nil

// src/runtime/runtime2.go:31（gstatus 常量片段）
const (
	_Gidle = iota // 0
	_Grunnable // 1
	_Grunning  // 2
	_Gsyscall  // 3
	_Gwaiting  // 4
	_Gmoribund_unused // 5
	_Gdead // 6
	_Genqueue_unused // 7
	_Gcopystack // 8
)

// src/runtime/runtime2.go:1224（waitReason 片段）
waitReasonZero                  waitReason = iota // ""
waitReasonGCAssistWait                            // "GC assist wait"
waitReasonSelect                                  // "select"
waitReasonChanReceive                             // "chan receive"
waitReasonSyncWaitGroupWait                       // "sync.WaitGroup.Wait"

grep -n "^func gopark\|^func goready\|^func execute\|^func goschedImpl\|^func goexit0" proc.go

457:func gopark(unlockf func(*g, unsafe.Pointer) bool, lock unsafe.Pointer, reason waitReason, traceReason traceBlockReason, traceskip int) {
493:func goready(gp *g, traceskip int) {
3346:func execute(gp *g, inheritTime bool) {
4322:func goschedImpl(gp *g, preempted bool) {
4506:func goexit0(gp *g) {

3360:	casgstatus(gp, _Grunnable, _Grunning)   // execute：即将运行
4290:	casgstatus(gp, _Grunning, _Gwaiting)    // gopark：主动阻塞
1145:	casgstatus(gp, _Gwaiting, _Grunnable)   // goready：被唤醒

// src/runtime/runtime2.go:471（g 结构体片段）
type g struct {
	stack       stack   // 该 goroutine 的栈区间 [lo, hi)
	m           *m      // 当前绑定的 M（仅 _Grunning/_Gsyscall 非空）
	atomicstatus atomic.Uint32 // 上面那张 gstatus 表的取值
	goid         uint64        // goroutine id，scheddetail 里的 "G23" 就是它
	waitsince    int64      // 进入阻塞的近似时刻
	waitreason   waitReason // 阻塞原因，scheddetail 括号里的文字
	preempt      bool       // 抢占信号，重复 stackguard0 = stackpreempt
}