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newproc获取新的goroutine#xff0c;并放置到P运行队列中 这也是go关键字之后实际编译调用的方法 func newproc(fn *funcval) {// 获取当前正在运行中的goroutinegp : getg()// 获取调用者的程序计数器地址#xff0c;用于调试和跟踪pc : getcallerp…
Gidle - Grunnable
newproc获取新的goroutine并放置到P运行队列中 这也是go关键字之后实际编译调用的方法 func newproc(fn *funcval) {// 获取当前正在运行中的goroutinegp : getg()// 获取调用者的程序计数器地址用于调试和跟踪pc : getcallerpc()systemstack(func() {// 创建一个新的 goroutine 并返回新创建的 goroutine 结构 newgnewg : newproc1(fn, gp, pc)// 获取当前P并将新创建的goroutine放到P的运行队列中pp : getg().m.p.ptr()runqput(pp, newg, true)// 如果主 goroutine 已经启动mainStarted 为 true则调用 wakep() 唤醒或启动一个处理器以执行运行队列中的 goroutineif mainStarted {wakep()}})
}newproc1用于获取新的goroutine
// Create a new g in state _Grunnable, starting at fn. callerpc is the
// address of the go statement that created this. The caller is responsible
// for adding the new g to the scheduler.
func newproc1(fn *funcval, callergp *g, callerpc uintptr) *g {if fn nil {fatal(go of nil func value)}mp : acquirem() // disable preemption because we hold M and P in local vars.pp : mp.p.ptr()// 首先从P的gfree获取回收的g如果没有那么再从全局调度器sched中gfree窃取给P再不然就只能调用malg()新建gnewg : gfget(pp)if newg nil {newg malg(stackMin)casgstatus(newg, _Gidle, _Gdead)allgadd(newg) // publishes with a g-status of Gdead so GC scanner doesnt look at uninitialized stack.}if newg.stack.hi 0 {throw(newproc1: newg missing stack)}if readgstatus(newg) ! _Gdead {throw(newproc1: new g is not Gdead)}// 计算和分配堆栈指针totalSize : uintptr(4*goarch.PtrSize sys.MinFrameSize) // extra space in case of reads slightly beyond frametotalSize alignUp(totalSize, sys.StackAlign)sp : newg.stack.hi - totalSizeif usesLR {// callers LR*(*uintptr)(unsafe.Pointer(sp)) 0prepGoExitFrame(sp)}if GOARCH arm64 {// callers FP*(*uintptr)(unsafe.Pointer(sp - goarch.PtrSize)) 0}// 初始化调用帧memclrNoHeapPointers(unsafe.Pointer(newg.sched), unsafe.Sizeof(newg.sched))newg.sched.sp spnewg.stktopsp spnewg.sched.pc abi.FuncPCABI0(goexit) sys.PCQuantum // PCQuantum so that previous instruction is in same functionnewg.sched.g guintptr(unsafe.Pointer(newg))gostartcallfn(newg.sched, fn)// 设置新G元数据newg.parentGoid callergp.goidnewg.gopc callerpcnewg.ancestors saveAncestors(callergp)newg.startpc fn.fnif isSystemGoroutine(newg, false) {sched.ngsys.Add(1)} else {// Only user goroutines inherit pprof labels.if mp.curg ! nil {newg.labels mp.curg.labels}if goroutineProfile.active {// A concurrent goroutine profile is running. It should include// exactly the set of goroutines that were alive when the goroutine// profiler first stopped the world. That does not include newg, so// mark it as not needing a profile before transitioning it from// _Gdead.newg.goroutineProfiled.Store(goroutineProfileSatisfied)}}// Track initial transition?newg.trackingSeq uint8(cheaprand())if newg.trackingSeq%gTrackingPeriod 0 {newg.tracking true}gcController.addScannableStack(pp, int64(newg.stack.hi-newg.stack.lo))// Get a goid and switch to runnable. Make all this atomic to the tracer.// 分配gid并更新状态为_Grunnabletrace : traceAcquire()casgstatus(newg, _Gdead, _Grunnable)if pp.goidcache pp.goidcacheend {// Sched.goidgen is the last allocated id,// this batch must be [sched.goidgen1, sched.goidgenGoidCacheBatch].// At startup sched.goidgen0, so main goroutine receives goid1.pp.goidcache sched.goidgen.Add(_GoidCacheBatch)pp.goidcache - _GoidCacheBatch - 1pp.goidcacheend pp.goidcache _GoidCacheBatch}newg.goid pp.goidcachepp.goidcachenewg.trace.reset()if trace.ok() {trace.GoCreate(newg, newg.startpc)traceRelease(trace)}// Set up race context.if raceenabled {newg.racectx racegostart(callerpc)newg.raceignore 0if newg.labels ! nil {// See note in proflabel.go on labelSyncs role in synchronizing// with the reads in the signal handler.racereleasemergeg(newg, unsafe.Pointer(labelSync))}}releasem(mp)return newg
}malg 创建新goroutine
主要就是分配了goroutine栈空间
// Allocate a new g, with a stack big enough for stacksize bytes.
func malg(stacksize int32) *g {newg : new(g)if stacksize 0 {stacksize round2(stackSystem stacksize)systemstack(func() {newg.stack stackalloc(uint32(stacksize))})newg.stackguard0 newg.stack.lo stackGuardnewg.stackguard1 ^uintptr(0)// Clear the bottom word of the stack. We record g// there on gsignal stack during VDSO on ARM and ARM64.*(*uintptr)(unsafe.Pointer(newg.stack.lo)) 0}return newg
}
runqput g置P中
先尝试放高优先的runnext槽中然后放P本地队列实在不行就放全局队列
// runqput tries to put g on the local runnable queue.
// If next is false, runqput adds g to the tail of the runnable queue.
// If next is true, runqput puts g in the pp.runnext slot.
// If the run queue is full, runnext puts g on the global queue.
// Executed only by the owner P.
func runqput(pp *p, gp *g, next bool) {if randomizeScheduler next randn(2) 0 {next false}// 如果next为真则尝试将gp发到pp.runnext中如果有正在操作的再进行尝试if next {retryNext:oldnext : pp.runnextif !pp.runnext.cas(oldnext, guintptr(unsafe.Pointer(gp))) {goto retryNext}if oldnext 0 {return}// Kick the old runnext out to the regular run queue.// 如果已经有goroutine则踢出并放入常规运行队列gp oldnext.ptr()}// 加入常规运行队列
retry:// 加载运行队列的头指针和尾指针h : atomic.LoadAcq(pp.runqhead) // load-acquire, synchronize with consumerst : pp.runqtail// 如果队列未满则将gp直接放入队列中if t-h uint32(len(pp.runq)) {pp.runq[t%uint32(len(pp.runq))].set(gp)atomic.StoreRel(pp.runqtail, t1) // store-release, makes the item available for consumptionreturn}// 如果队列已满则尝试慢策略if runqputslow(pp, gp, h, t) {return}// the queue is not full, now the put above must succeedgoto retry
}
runqputslow将一次性将本地队列中的多个g放入到全局队列中
// Put g and a batch of work from local runnable queue on global queue.
// Executed only by the owner P.
func runqputslow(pp *p, gp *g, h, t uint32) bool {var batch [len(pp.runq)/2 1]*g// First, grab a batch from local queue.// 先从本地队列中抓取一批gn : t - hn n / 2if n ! uint32(len(pp.runq)/2) {throw(runqputslow: queue is not full)}for i : uint32(0); i n; i {batch[i] pp.runq[(hi)%uint32(len(pp.runq))].ptr()}// 如果cas失败说明已经有其它工作线程从_p_的本地运行队列偷走了一些goroutine所以直接返回if !atomic.CasRel(pp.runqhead, h, hn) { // cas-release, commits consumereturn false}batch[n] gpif randomizeScheduler {for i : uint32(1); i n; i {j : cheaprandn(i 1)batch[i], batch[j] batch[j], batch[i]}}// 将需要放入全局运行队列的g连起来减少后面对全局链表的锁住时间从而降低锁冲突// Link the goroutines.for i : uint32(0); i n; i {batch[i].schedlink.set(batch[i1])}var q gQueueq.head.set(batch[0])q.tail.set(batch[n])// Now put the batch on global queue.// 将链表放入全局队列中lock(sched.lock)globrunqputbatch(q, int32(n1))unlock(sched.lock)return true
}
Grunnable - Gruning
将指定的goroutine绑定到当前M上其状态设置为运行然后运行实际代码
func execute(gp *g, inheritTime bool) {// 获取当前正在运行的Mmp : getg().m// 如果goroutine是活跃的那么尝试记录当前goroutine的堆栈信息if goroutineProfile.active {tryRecordGoroutineProfile(gp, osyield)}// goroutine与M相互绑定并更新goroutine为运行态mp.curg gpgp.m mpcasgstatus(gp, _Grunnable, _Grunning)// 初始化goroutine其他信息gp.waitsince 0gp.preempt falsegp.stackguard0 gp.stack.lo stackGuardif !inheritTime {mp.p.ptr().schedtick}// Check whether the profiler needs to be turned on or off.hz : sched.profilehzif mp.profilehz ! hz {setThreadCPUProfiler(hz)}trace : traceAcquire()if trace.ok() {// GoSysExit has to happen when we have a P, but before GoStart.// So we emit it here.if !goexperiment.ExecTracer2 gp.syscallsp ! 0 {trace.GoSysExit(true)}trace.GoStart()traceRelease(trace)}// 切换到goroutine调度上下文实际执行goroutine代码// 就是从g0切换到g栈空间并执行g的用户代码gogo(gp.sched)
}
Gruning - Gdead
对普通M不是M0而言执行完任务之后会进行到goexit并等待重新调度
// Finishes execution of the current goroutine.
func goexit1() {if raceenabled {racegoend()}trace : traceAcquire()if trace.ok() {trace.GoEnd()traceRelease(trace)}mcall(goexit0)
}// goexit continuation on g0.
func goexit0(gp *g) {// 销毁gdestroy(gp)// 调度查找一个可运行的goroutine并执行schedule()
}gdestroy 销毁goroutine
销毁其实就是更新状态为Gdead清除goroutine数据重新放回P空闲池中
func gdestroy(gp *g) {// 获取当前M与Pmp : getg().mpp : mp.p.ptr()// 更新goroutine状态为Gdeadcasgstatus(gp, _Grunning, _Gdead)// 更新GC控制器。减少可扫描的堆栈大小gcController.addScannableStack(pp, -int64(gp.stack.hi-gp.stack.lo))// 如果是系统goroutine减少计数if isSystemGoroutine(gp, false) {sched.ngsys.Add(-1)}// 清除goroutine状态gp.m nillocked : gp.lockedm ! 0gp.lockedm 0mp.lockedg 0gp.preemptStop falsegp.paniconfault falsegp._defer nil // should be true already but just in case.gp._panic nil // non-nil for Goexit during panic. points at stack-allocated data.gp.writebuf nilgp.waitreason waitReasonZerogp.param nilgp.labels nilgp.timer nilif gcBlackenEnabled ! 0 gp.gcAssistBytes 0 {// Flush assist credit to the global pool. This gives// better information to pacing if the application is// rapidly creating an exiting goroutines.assistWorkPerByte : gcController.assistWorkPerByte.Load()scanCredit : int64(assistWorkPerByte * float64(gp.gcAssistBytes))gcController.bgScanCredit.Add(scanCredit)gp.gcAssistBytes 0}// 释放当前M的goroutinedropg()if GOARCH wasm { // no threads yet on wasmgfput(pp, gp)return}if mp.lockedInt ! 0 {print(invalid m-lockedInt , mp.lockedInt, \n)throw(internal lockOSThread error)}// 将 goroutine 放回空闲池gfput(pp, gp)if locked {// The goroutine may have locked this thread because// it put it in an unusual kernel state. Kill it// rather than returning it to the thread pool.// Return to mstart, which will release the P and exit// the thread.if GOOS ! plan9 { // See golang.org/issue/22227.gogo(mp.g0.sched)} else {// Clear lockedExt on plan9 since we may end up re-using// this thread.mp.lockedExt 0}}
}Grunning - Gwaiting
park_m主要负责将当前的 goroutine 暂停切换其状态并在必要时重新调度执行
// park continuation on g0.
func park_m(gp *g) {mp : getg().mtrace : traceAcquire()// N.B. Not using casGToWaiting here because the waitreason is// set by park_ms caller.// 更改goroutine状态从Grunning到Gwaitingcasgstatus(gp, _Grunning, _Gwaiting)if trace.ok() {trace.GoPark(mp.waitTraceBlockReason, mp.waitTraceSkip)traceRelease(trace)}// 将当前goroutine与M分离dropg()// 确保在某些条件下安全地将 Goroutine 从等待状态移出处理失败的解锁操作并在必要时重新调度该 Goroutine// 调用解锁函数if fn : mp.waitunlockf; fn ! nil {ok : fn(gp, mp.waitlock)mp.waitunlockf nilmp.waitlock nilif !ok {trace : traceAcquire()casgstatus(gp, _Gwaiting, _Grunnable)if trace.ok() {trace.GoUnpark(gp, 2)traceRelease(trace)}execute(gp, true) // Schedule it back, never returns.}}// 调度切换到其他 goroutine 执行schedule()
}Gwaiting - Grunable
ready将指定的 goroutine 标记为可运行状态并将其放入运行队列中
// Mark gp ready to run.
func ready(gp *g, traceskip int, next bool) {// 读取 gp 的当前状态status : readgstatus(gp)// 标记为可运行// Mark runnable.mp : acquirem() // disable preemption because it can be holding p in a local varif status^_Gscan ! _Gwaiting {dumpgstatus(gp)throw(bad g-status in ready)}// status is Gwaiting or Gscanwaiting, make Grunnable and put on runqtrace : traceAcquire()casgstatus(gp, _Gwaiting, _Grunnable)if trace.ok() {trace.GoUnpark(gp, traceskip)traceRelease(trace)}// 将 gp 放入当前 P 的运行队列中。如果 next 为 true表示将 gp 放在队列的前面否则放在队列的后面runqput(mp.p.ptr(), gp, next)// 确保有一个 P 可以运行 gpwakep()// 重新启用当前M的抢占releasem(mp)
}
Grunning - Grunnable
goschedImpl 函数用于将当前 goroutine 交出 CPU使其重新排队等待调度执行。它的实现涉及状态检查、状态变更、跟踪信息处理、全局运行队列操作和重新调度
goschedImpl 函数执行的主要步骤包括
获取并验证 gp 的当前状态。将 gp 的状态修改为 _Grunnable表示它现在是可运行状态。解绑当前 M 和 gp。获取调度器锁并将 gp 放入全局运行队列。如果主 goroutine 已经启动则唤醒一个 P 以确保运行队列中的 goroutine 被处理。重新进入调度循环选择下一个可运行的 goroutine 开始执行。
func goschedImpl(gp *g, preempted bool) {trace : traceAcquire()status : readgstatus(gp)if status^_Gscan ! _Grunning {dumpgstatus(gp)throw(bad g status)}casgstatus(gp, _Grunning, _Grunnable)if trace.ok() {if preempted {trace.GoPreempt()} else {trace.GoSched()}traceRelease(trace)}dropg()lock(sched.lock)globrunqput(gp)unlock(sched.lock)if mainStarted {wakep()}schedule()
}大致总结下 go池是所有拥有goroutine的地方包括P的runnext、P本地队列和全局队列 Gidle - Grunnable: 初始化g放入go池Grunnable - Grunning: 从go池取出绑定M执行实际代码Grunning - Gdead: 解绑M重置g重新放入go池- Gwaiting: 解绑M等待被唤醒- Grunnable: 解绑M放入go全局队列 Gwaiting - Grunable: 被唤醒后放入go池
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