goroutine
Goroutine
https://github.com/golang/go/blob/master/src/runtime/runtime2.go
G
// G 结构体
type g struct {
// Stack parameters.
// stack describes the actual stack memory: [stack.lo, stack.hi).
// stackguard0 is the stack pointer compared in the Go stack growth prologue.
// It is stack.lo+StackGuard normally, but can be StackPreempt to trigger a preemption.
// stackguard1 is the stack pointer compared in the C stack growth prologue.
// It is stack.lo+StackGuard on g0 and gsignal stacks.
// It is ~0 on other goroutine stacks, to trigger a call to morestackc (and crash).
stack stack // offset known to runtime/cgo
stackguard0 uintptr // offset known to liblink
stackguard1 uintptr // offset known to liblink
_panic *_panic // innermost panic - offset known to liblink
_defer *_defer // innermost defer
m *m // current m; offset known to arm liblink
sched gobuf
syscallsp uintptr // if status==Gsyscall, syscallsp = sched.sp to use during gc
syscallpc uintptr // if status==Gsyscall, syscallpc = sched.pc to use during gc
stktopsp uintptr // expected sp at top of stack, to check in traceback
// param is a generic pointer parameter field used to pass
// values in particular contexts where other storage for the
// parameter would be difficult to find. It is currently used
// in three ways:
// 1. When a channel operation wakes up a blocked goroutine, it sets param to
// point to the sudog of the completed blocking operation.
// 2. By gcAssistAlloc1 to signal back to its caller that the goroutine completed
// the GC cycle. It is unsafe to do so in any other way, because the goroutine's
// stack may have moved in the meantime.
// 3. By debugCallWrap to pass parameters to a new goroutine because allocating a
// closure in the runtime is forbidden.
param unsafe.Pointer
atomicstatus uint32
stackLock uint32 // sigprof/scang lock; TODO: fold in to atomicstatus
goid int64
schedlink guintptr
waitsince int64 // approx time when the g become blocked
waitreason waitReason // if status==Gwaiting
preempt bool // preemption signal, duplicates stackguard0 = stackpreempt
preemptStop bool // transition to _Gpreempted on preemption; otherwise, just deschedule
preemptShrink bool // shrink stack at synchronous safe point
// asyncSafePoint is set if g is stopped at an asynchronous
// safe point. This means there are frames on the stack
// without precise pointer information.
asyncSafePoint bool
paniconfault bool // panic (instead of crash) on unexpected fault address
gcscandone bool // g has scanned stack; protected by _Gscan bit in status
throwsplit bool // must not split stack
// activeStackChans indicates that there are unlocked channels
// pointing into this goroutine's stack. If true, stack
// copying needs to acquire channel locks to protect these
// areas of the stack.
activeStackChans bool
// parkingOnChan indicates that the goroutine is about to
// park on a chansend or chanrecv. Used to signal an unsafe point
// for stack shrinking. It's a boolean value, but is updated atomically.
parkingOnChan uint8
raceignore int8 // ignore race detection events
sysblocktraced bool // StartTrace has emitted EvGoInSyscall about this goroutine
tracking bool // whether we're tracking this G for sched latency statistics
trackingSeq uint8 // used to decide whether to track this G
runnableStamp int64 // timestamp of when the G last became runnable, only used when tracking
runnableTime int64 // the amount of time spent runnable, cleared when running, only used when tracking
sysexitticks int64 // cputicks when syscall has returned (for tracing)
traceseq uint64 // trace event sequencer
tracelastp puintptr // last P emitted an event for this goroutine
lockedm muintptr
sig uint32
writebuf []byte
sigcode0 uintptr
sigcode1 uintptr
sigpc uintptr
gopc uintptr // pc of go statement that created this goroutine
ancestors *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
startpc uintptr // pc of goroutine function
racectx uintptr
waiting *sudog // sudog structures this g is waiting on (that have a valid elem ptr); in lock order
cgoCtxt []uintptr // cgo traceback context
labels unsafe.Pointer // profiler labels
timer *timer // cached timer for time.Sleep
selectDone uint32 // are we participating in a select and did someone win the race?
// goroutineProfiled indicates the status of this goroutine's stack for the
// current in-progress goroutine profile
goroutineProfiled goroutineProfileStateHolder
// Per-G GC state
// gcAssistBytes is this G's GC assist credit in terms of
// bytes allocated. If this is positive, then the G has credit
// to allocate gcAssistBytes bytes without assisting. If this
// is negative, then the G must correct this by performing
// scan work. We track this in bytes to make it fast to update
// and check for debt in the malloc hot path. The assist ratio
// determines how this corresponds to scan work debt.
gcAssistBytes int64
}
// Machine
type m struct {
g0 *g // goroutine with scheduling stack
morebuf gobuf // gobuf arg to morestack
divmod uint32 // div/mod denominator for arm - known to liblink
_ uint32 // align next field to 8 bytes
// Fields not known to debuggers.
procid uint64 // for debuggers, but offset not hard-coded
gsignal *g // signal-handling g
goSigStack gsignalStack // Go-allocated signal handling stack
sigmask sigset // storage for saved signal mask
tls [tlsSlots]uintptr // thread-local storage (for x86 extern register)
mstartfn func()
curg *g // current running goroutine
caughtsig guintptr // goroutine running during fatal signal
p puintptr // attached p for executing go code (nil if not executing go code)
nextp puintptr
oldp puintptr // the p that was attached before executing a syscall
id int64
mallocing int32
throwing throwType
preemptoff string // if != "", keep curg running on this m
locks int32
dying int32
profilehz int32
spinning bool // m is out of work and is actively looking for work
blocked bool // m is blocked on a note
newSigstack bool // minit on C thread called sigaltstack
printlock int8
incgo bool // m is executing a cgo call
freeWait uint32 // if == 0, safe to free g0 and delete m (atomic)
fastrand uint64
needextram bool
traceback uint8
ncgocall uint64 // number of cgo calls in total
ncgo int32 // number of cgo calls currently in progress
cgoCallersUse uint32 // if non-zero, cgoCallers in use temporarily
cgoCallers *cgoCallers // cgo traceback if crashing in cgo call
park note
alllink *m // on allm
schedlink muintptr
lockedg guintptr
createstack [32]uintptr // stack that created this thread.
lockedExt uint32 // tracking for external LockOSThread
lockedInt uint32 // tracking for internal lockOSThread
nextwaitm muintptr // next m waiting for lock
waitunlockf func(*g, unsafe.Pointer) bool
waitlock unsafe.Pointer
waittraceev byte
waittraceskip int
startingtrace bool
syscalltick uint32
freelink *m // on sched.freem
// these are here because they are too large to be on the stack
// of low-level NOSPLIT functions.
libcall libcall
libcallpc uintptr // for cpu profiler
libcallsp uintptr
libcallg guintptr
syscall libcall // stores syscall parameters on windows
vdsoSP uintptr // SP for traceback while in VDSO call (0 if not in call)
vdsoPC uintptr // PC for traceback while in VDSO call
// preemptGen counts the number of completed preemption
// signals. This is used to detect when a preemption is
// requested, but fails. Accessed atomically.
preemptGen uint32
// Whether this is a pending preemption signal on this M.
// Accessed atomically.
signalPending uint32
dlogPerM
mOS
// Up to 10 locks held by this m, maintained by the lock ranking code.
locksHeldLen int
locksHeld [10]heldLockInfo
}
work-strealing
runtime.schedule() {
// only 1/61 of the time, check the global runnable queue for a G.
// if not found, check the local queue.
// if not found,
// try to steal from other Ps.
// if not, check the global runnable queue.
// if not found, poll network.
}
调度策略
https://github.com/lifei6671/interview-go/blob/master/base/go-scheduler.md