mirror of
https://github.com/golang/go
synced 2024-11-12 07:40:23 -07:00
time: allow cancelling of After events.
Also simplify sleeper algorithm and poll occasionally so redundant sleeper goroutines will quit sooner. R=r, niemeyer, r2 CC=golang-dev https://golang.org/cl/4063043
This commit is contained in:
parent
66905bd9ac
commit
2ae953bfc3
@ -11,20 +11,40 @@ import (
|
||||
"container/heap"
|
||||
)
|
||||
|
||||
// The event type represents a single After or AfterFunc event.
|
||||
type event struct {
|
||||
t int64 // The absolute time that the event should fire.
|
||||
f func(int64) // The function to call when the event fires.
|
||||
sleeping bool // A sleeper is sleeping for this event.
|
||||
// The Timer type represents a single event.
|
||||
// When the Timer expires, the current time will be sent on C
|
||||
// unless the Timer represents an AfterFunc event.
|
||||
type Timer struct {
|
||||
C <-chan int64
|
||||
t int64 // The absolute time that the event should fire.
|
||||
f func(int64) // The function to call when the event fires.
|
||||
i int // The event's index inside eventHeap.
|
||||
}
|
||||
|
||||
type eventHeap []*event
|
||||
type timerHeap []*Timer
|
||||
|
||||
var events eventHeap
|
||||
var eventMutex sync.Mutex
|
||||
// forever is the absolute time (in ns) of an event that is forever away.
|
||||
const forever = 1 << 62
|
||||
|
||||
// maxSleepTime is the maximum length of time that a sleeper
|
||||
// sleeps for before checking if it is defunct.
|
||||
const maxSleepTime = 1e9
|
||||
|
||||
var (
|
||||
// timerMutex guards the variables inside this var group.
|
||||
timerMutex sync.Mutex
|
||||
|
||||
// timers holds a binary heap of pending events, terminated with a sentinel.
|
||||
timers timerHeap
|
||||
|
||||
// currentSleeper is an ever-incrementing counter which represents
|
||||
// the current sleeper. It allows older sleepers to detect that they are
|
||||
// defunct and exit.
|
||||
currentSleeper int64
|
||||
)
|
||||
|
||||
func init() {
|
||||
events.Push(&event{1 << 62, nil, true}) // sentinel
|
||||
timers.Push(&Timer{t: forever}) // sentinel
|
||||
}
|
||||
|
||||
// Sleep pauses the current goroutine for at least ns nanoseconds.
|
||||
@ -51,101 +71,133 @@ func sleep(t, ns int64) (int64, os.Error) {
|
||||
return t, nil
|
||||
}
|
||||
|
||||
// NewTimer creates a new Timer that will send
|
||||
// the current time on its channel after at least ns nanoseconds.
|
||||
func NewTimer(ns int64) *Timer {
|
||||
c := make(chan int64, 1)
|
||||
e := after(ns, func(t int64) { c <- t })
|
||||
e.C = c
|
||||
return e
|
||||
}
|
||||
|
||||
// After waits at least ns nanoseconds before sending the current time
|
||||
// on the returned channel.
|
||||
// It is equivalent to NewTimer(ns).C.
|
||||
func After(ns int64) <-chan int64 {
|
||||
c := make(chan int64, 1)
|
||||
after(ns, func(t int64) { c <- t })
|
||||
return c
|
||||
return NewTimer(ns).C
|
||||
}
|
||||
|
||||
// AfterFunc waits at least ns nanoseconds before calling f
|
||||
// in its own goroutine.
|
||||
func AfterFunc(ns int64, f func()) {
|
||||
after(ns, func(_ int64) {
|
||||
// in its own goroutine. It returns a Timer that can
|
||||
// be used to cancel the call using its Stop method.
|
||||
func AfterFunc(ns int64, f func()) *Timer {
|
||||
return after(ns, func(_ int64) {
|
||||
go f()
|
||||
})
|
||||
}
|
||||
|
||||
// Stop prevents the Timer from firing.
|
||||
// It returns true if the call stops the timer, false if the timer has already
|
||||
// expired or stopped.
|
||||
func (e *Timer) Stop() (ok bool) {
|
||||
timerMutex.Lock()
|
||||
// Avoid removing the first event in the queue so that
|
||||
// we don't start a new sleeper unnecessarily.
|
||||
if e.i > 0 {
|
||||
heap.Remove(timers, e.i)
|
||||
}
|
||||
ok = e.f != nil
|
||||
e.f = nil
|
||||
timerMutex.Unlock()
|
||||
return
|
||||
}
|
||||
|
||||
// after is the implementation of After and AfterFunc.
|
||||
// When the current time is after ns, it calls f with the current time.
|
||||
// It assumes that f will not block.
|
||||
func after(ns int64, f func(int64)) {
|
||||
func after(ns int64, f func(int64)) (e *Timer) {
|
||||
now := Nanoseconds()
|
||||
t := Nanoseconds() + ns
|
||||
eventMutex.Lock()
|
||||
t0 := events[0].t
|
||||
heap.Push(events, &event{t, f, false})
|
||||
if t < t0 {
|
||||
go sleeper()
|
||||
if ns > 0 && t < now {
|
||||
panic("time: time overflow")
|
||||
}
|
||||
eventMutex.Unlock()
|
||||
timerMutex.Lock()
|
||||
t0 := timers[0].t
|
||||
e = &Timer{nil, t, f, -1}
|
||||
heap.Push(timers, e)
|
||||
// Start a new sleeper if the new event is before
|
||||
// the first event in the queue. If the length of time
|
||||
// until the new event is at least maxSleepTime,
|
||||
// then we're guaranteed that the sleeper will wake up
|
||||
// in time to service it, so no new sleeper is needed.
|
||||
if t0 > t && (t0 == forever || ns < maxSleepTime) {
|
||||
currentSleeper++
|
||||
go sleeper(currentSleeper)
|
||||
}
|
||||
timerMutex.Unlock()
|
||||
return
|
||||
}
|
||||
|
||||
// sleeper continually looks at the earliest event in the queue, marks it
|
||||
// as sleeping, waits until it happens, then removes any events
|
||||
// in the queue that are due. It stops when it finds an event that is
|
||||
// already marked as sleeping. When an event is inserted before the first item,
|
||||
// a new sleeper is started.
|
||||
//
|
||||
// Scheduling vagaries mean that sleepers may not wake up in
|
||||
// exactly the order of the events that they are waiting for,
|
||||
// but this does not matter as long as there are at least as
|
||||
// many sleepers as events marked sleeping (invariant). This ensures that
|
||||
// there is always a sleeper to service the remaining events.
|
||||
//
|
||||
// A sleeper will remove at least the event it has been waiting for
|
||||
// unless the event has already been removed by another sleeper. Both
|
||||
// cases preserve the invariant described above.
|
||||
func sleeper() {
|
||||
eventMutex.Lock()
|
||||
e := events[0]
|
||||
for !e.sleeping {
|
||||
t := Nanoseconds()
|
||||
// sleeper continually looks at the earliest event in the queue, waits until it happens,
|
||||
// then removes any events in the queue that are due. It stops when the queue
|
||||
// is empty or when another sleeper has been started.
|
||||
func sleeper(sleeperId int64) {
|
||||
timerMutex.Lock()
|
||||
e := timers[0]
|
||||
t := Nanoseconds()
|
||||
for e.t != forever {
|
||||
if dt := e.t - t; dt > 0 {
|
||||
e.sleeping = true
|
||||
eventMutex.Unlock()
|
||||
if nt, err := sleep(t, dt); err != nil {
|
||||
// If sleep has encountered an error,
|
||||
// there's not much we can do. We pretend
|
||||
// that time really has advanced by the required
|
||||
// amount and lie to the rest of the system.
|
||||
t = e.t
|
||||
} else {
|
||||
t = nt
|
||||
if dt > maxSleepTime {
|
||||
dt = maxSleepTime
|
||||
}
|
||||
timerMutex.Unlock()
|
||||
syscall.Sleep(dt)
|
||||
timerMutex.Lock()
|
||||
if currentSleeper != sleeperId {
|
||||
// Another sleeper has been started, making this one redundant.
|
||||
break
|
||||
}
|
||||
eventMutex.Lock()
|
||||
e = events[0]
|
||||
}
|
||||
e = timers[0]
|
||||
t = Nanoseconds()
|
||||
for t >= e.t {
|
||||
e.f(t)
|
||||
heap.Pop(events)
|
||||
e = events[0]
|
||||
if e.f != nil {
|
||||
e.f(t)
|
||||
e.f = nil
|
||||
}
|
||||
heap.Pop(timers)
|
||||
e = timers[0]
|
||||
}
|
||||
}
|
||||
eventMutex.Unlock()
|
||||
timerMutex.Unlock()
|
||||
}
|
||||
|
||||
func (eventHeap) Len() int {
|
||||
return len(events)
|
||||
func (timerHeap) Len() int {
|
||||
return len(timers)
|
||||
}
|
||||
|
||||
func (eventHeap) Less(i, j int) bool {
|
||||
return events[i].t < events[j].t
|
||||
func (timerHeap) Less(i, j int) bool {
|
||||
return timers[i].t < timers[j].t
|
||||
}
|
||||
|
||||
func (eventHeap) Swap(i, j int) {
|
||||
events[i], events[j] = events[j], events[i]
|
||||
func (timerHeap) Swap(i, j int) {
|
||||
timers[i], timers[j] = timers[j], timers[i]
|
||||
timers[i].i = i
|
||||
timers[j].i = j
|
||||
}
|
||||
|
||||
func (eventHeap) Push(x interface{}) {
|
||||
events = append(events, x.(*event))
|
||||
func (timerHeap) Push(x interface{}) {
|
||||
e := x.(*Timer)
|
||||
e.i = len(timers)
|
||||
timers = append(timers, e)
|
||||
}
|
||||
|
||||
func (eventHeap) Pop() interface{} {
|
||||
func (timerHeap) Pop() interface{} {
|
||||
// TODO: possibly shrink array.
|
||||
n := len(events) - 1
|
||||
e := events[n]
|
||||
events[n] = nil
|
||||
events = events[0:n]
|
||||
n := len(timers) - 1
|
||||
e := timers[n]
|
||||
timers[n] = nil
|
||||
timers = timers[0:n]
|
||||
e.i = -1
|
||||
return e
|
||||
}
|
||||
|
@ -64,6 +64,18 @@ func BenchmarkAfterFunc(b *testing.B) {
|
||||
<-c
|
||||
}
|
||||
|
||||
func BenchmarkAfter(b *testing.B) {
|
||||
for i := 0; i < b.N; i++ {
|
||||
<-After(1)
|
||||
}
|
||||
}
|
||||
|
||||
func BenchmarkStop(b *testing.B) {
|
||||
for i := 0; i < b.N; i++ {
|
||||
NewTimer(1e9).Stop()
|
||||
}
|
||||
}
|
||||
|
||||
func TestAfter(t *testing.T) {
|
||||
const delay = int64(100e6)
|
||||
start := Nanoseconds()
|
||||
@ -94,6 +106,30 @@ func TestAfterTick(t *testing.T) {
|
||||
}
|
||||
}
|
||||
|
||||
func TestAfterStop(t *testing.T) {
|
||||
const msec = 1e6
|
||||
AfterFunc(100*msec, func() {})
|
||||
t0 := NewTimer(50 * msec)
|
||||
c1 := make(chan bool, 1)
|
||||
t1 := AfterFunc(150*msec, func() { c1 <- true })
|
||||
c2 := After(200 * msec)
|
||||
if !t0.Stop() {
|
||||
t.Fatalf("failed to stop event 0")
|
||||
}
|
||||
if !t1.Stop() {
|
||||
t.Fatalf("failed to stop event 1")
|
||||
}
|
||||
<-c2
|
||||
_, ok0 := <-t0.C
|
||||
_, ok1 := <-c1
|
||||
if ok0 || ok1 {
|
||||
t.Fatalf("events were not stopped")
|
||||
}
|
||||
if t1.Stop() {
|
||||
t.Fatalf("Stop returned true twice")
|
||||
}
|
||||
}
|
||||
|
||||
var slots = []int{5, 3, 6, 6, 6, 1, 1, 2, 7, 9, 4, 8, 0}
|
||||
|
||||
type afterResult struct {
|
||||
|
@ -43,3 +43,14 @@ func TestTeardown(t *testing.T) {
|
||||
ticker.Stop()
|
||||
}
|
||||
}
|
||||
|
||||
func BenchmarkTicker(b *testing.B) {
|
||||
ticker := NewTicker(1)
|
||||
b.ResetTimer()
|
||||
b.StartTimer()
|
||||
for i := 0; i < b.N; i++ {
|
||||
<-ticker.C
|
||||
}
|
||||
b.StopTimer()
|
||||
ticker.Stop()
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user