Current File : //usr/local/go/src/time/sleep_test.go
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package time_test
import (
"errors"
"fmt"
"math/rand"
"runtime"
"strings"
"sync"
"sync/atomic"
"testing"
. "time"
)
// Go runtime uses different Windows timers for time.Now and sleeping.
// These can tick at different frequencies and can arrive out of sync.
// The effect can be seen, for example, as time.Sleep(100ms) is actually
// shorter then 100ms when measured as difference between time.Now before and
// after time.Sleep call. This was observed on Windows XP SP3 (windows/386).
// windowsInaccuracy is to ignore such errors.
const windowsInaccuracy = 17 * Millisecond
func TestSleep(t *testing.T) {
const delay = 100 * Millisecond
go func() {
Sleep(delay / 2)
Interrupt()
}()
start := Now()
Sleep(delay)
delayadj := delay
if runtime.GOOS == "windows" {
delayadj -= windowsInaccuracy
}
duration := Now().Sub(start)
if duration < delayadj {
t.Fatalf("Sleep(%s) slept for only %s", delay, duration)
}
}
// Test the basic function calling behavior. Correct queueing
// behavior is tested elsewhere, since After and AfterFunc share
// the same code.
func TestAfterFunc(t *testing.T) {
i := 10
c := make(chan bool)
var f func()
f = func() {
i--
if i >= 0 {
AfterFunc(0, f)
Sleep(1 * Second)
} else {
c <- true
}
}
AfterFunc(0, f)
<-c
}
func TestAfterStress(t *testing.T) {
stop := uint32(0)
go func() {
for atomic.LoadUint32(&stop) == 0 {
runtime.GC()
// Yield so that the OS can wake up the timer thread,
// so that it can generate channel sends for the main goroutine,
// which will eventually set stop = 1 for us.
Sleep(Nanosecond)
}
}()
ticker := NewTicker(1)
for i := 0; i < 100; i++ {
<-ticker.C
}
ticker.Stop()
atomic.StoreUint32(&stop, 1)
}
func benchmark(b *testing.B, bench func(n int)) {
// Create equal number of garbage timers on each P before starting
// the benchmark.
var wg sync.WaitGroup
garbageAll := make([][]*Timer, runtime.GOMAXPROCS(0))
for i := range garbageAll {
wg.Add(1)
go func(i int) {
defer wg.Done()
garbage := make([]*Timer, 1<<15)
for j := range garbage {
garbage[j] = AfterFunc(Hour, nil)
}
garbageAll[i] = garbage
}(i)
}
wg.Wait()
b.ResetTimer()
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
bench(1000)
}
})
b.StopTimer()
for _, garbage := range garbageAll {
for _, t := range garbage {
t.Stop()
}
}
}
func BenchmarkAfterFunc(b *testing.B) {
benchmark(b, func(n int) {
c := make(chan bool)
var f func()
f = func() {
n--
if n >= 0 {
AfterFunc(0, f)
} else {
c <- true
}
}
AfterFunc(0, f)
<-c
})
}
func BenchmarkAfter(b *testing.B) {
benchmark(b, func(n int) {
for i := 0; i < n; i++ {
<-After(1)
}
})
}
func BenchmarkStop(b *testing.B) {
benchmark(b, func(n int) {
for i := 0; i < n; i++ {
NewTimer(1 * Second).Stop()
}
})
}
func BenchmarkSimultaneousAfterFunc(b *testing.B) {
benchmark(b, func(n int) {
var wg sync.WaitGroup
wg.Add(n)
for i := 0; i < n; i++ {
AfterFunc(0, wg.Done)
}
wg.Wait()
})
}
func BenchmarkStartStop(b *testing.B) {
benchmark(b, func(n int) {
timers := make([]*Timer, n)
for i := 0; i < n; i++ {
timers[i] = AfterFunc(Hour, nil)
}
for i := 0; i < n; i++ {
timers[i].Stop()
}
})
}
func BenchmarkReset(b *testing.B) {
benchmark(b, func(n int) {
t := NewTimer(Hour)
for i := 0; i < n; i++ {
t.Reset(Hour)
}
t.Stop()
})
}
func BenchmarkSleep(b *testing.B) {
benchmark(b, func(n int) {
var wg sync.WaitGroup
wg.Add(n)
for i := 0; i < n; i++ {
go func() {
Sleep(Nanosecond)
wg.Done()
}()
}
wg.Wait()
})
}
func TestAfter(t *testing.T) {
const delay = 100 * Millisecond
start := Now()
end := <-After(delay)
delayadj := delay
if runtime.GOOS == "windows" {
delayadj -= windowsInaccuracy
}
if duration := Now().Sub(start); duration < delayadj {
t.Fatalf("After(%s) slept for only %d ns", delay, duration)
}
if min := start.Add(delayadj); end.Before(min) {
t.Fatalf("After(%s) expect >= %s, got %s", delay, min, end)
}
}
func TestAfterTick(t *testing.T) {
const Count = 10
Delta := 100 * Millisecond
if testing.Short() {
Delta = 10 * Millisecond
}
t0 := Now()
for i := 0; i < Count; i++ {
<-After(Delta)
}
t1 := Now()
d := t1.Sub(t0)
target := Delta * Count
if d < target*9/10 {
t.Fatalf("%d ticks of %s too fast: took %s, expected %s", Count, Delta, d, target)
}
if !testing.Short() && d > target*30/10 {
t.Fatalf("%d ticks of %s too slow: took %s, expected %s", Count, Delta, d, target)
}
}
func TestAfterStop(t *testing.T) {
// We want to test that we stop a timer before it runs.
// We also want to test that it didn't run after a longer timer.
// Since we don't want the test to run for too long, we don't
// want to use lengthy times. That makes the test inherently flaky.
// So only report an error if it fails five times in a row.
var errs []string
logErrs := func() {
for _, e := range errs {
t.Log(e)
}
}
for i := 0; i < 5; i++ {
AfterFunc(100*Millisecond, func() {})
t0 := NewTimer(50 * Millisecond)
c1 := make(chan bool, 1)
t1 := AfterFunc(150*Millisecond, func() { c1 <- true })
c2 := After(200 * Millisecond)
if !t0.Stop() {
errs = append(errs, "failed to stop event 0")
continue
}
if !t1.Stop() {
errs = append(errs, "failed to stop event 1")
continue
}
<-c2
select {
case <-t0.C:
errs = append(errs, "event 0 was not stopped")
continue
case <-c1:
errs = append(errs, "event 1 was not stopped")
continue
default:
}
if t1.Stop() {
errs = append(errs, "Stop returned true twice")
continue
}
// Test passed, so all done.
if len(errs) > 0 {
t.Logf("saw %d errors, ignoring to avoid flakiness", len(errs))
logErrs()
}
return
}
t.Errorf("saw %d errors", len(errs))
logErrs()
}
func TestAfterQueuing(t *testing.T) {
// This test flakes out on some systems,
// so we'll try it a few times before declaring it a failure.
const attempts = 5
err := errors.New("!=nil")
for i := 0; i < attempts && err != nil; i++ {
delta := Duration(20+i*50) * Millisecond
if err = testAfterQueuing(delta); err != nil {
t.Logf("attempt %v failed: %v", i, err)
}
}
if err != nil {
t.Fatal(err)
}
}
var slots = []int{5, 3, 6, 6, 6, 1, 1, 2, 7, 9, 4, 8, 0}
type afterResult struct {
slot int
t Time
}
func await(slot int, result chan<- afterResult, ac <-chan Time) {
result <- afterResult{slot, <-ac}
}
func testAfterQueuing(delta Duration) error {
// make the result channel buffered because we don't want
// to depend on channel queueing semantics that might
// possibly change in the future.
result := make(chan afterResult, len(slots))
t0 := Now()
for _, slot := range slots {
go await(slot, result, After(Duration(slot)*delta))
}
var order []int
var times []Time
for range slots {
r := <-result
order = append(order, r.slot)
times = append(times, r.t)
}
for i := range order {
if i > 0 && order[i] < order[i-1] {
return fmt.Errorf("After calls returned out of order: %v", order)
}
}
for i, t := range times {
dt := t.Sub(t0)
target := Duration(order[i]) * delta
if dt < target-delta/2 || dt > target+delta*10 {
return fmt.Errorf("After(%s) arrived at %s, expected [%s,%s]", target, dt, target-delta/2, target+delta*10)
}
}
return nil
}
func TestTimerStopStress(t *testing.T) {
if testing.Short() {
return
}
for i := 0; i < 100; i++ {
go func(i int) {
timer := AfterFunc(2*Second, func() {
t.Errorf("timer %d was not stopped", i)
})
Sleep(1 * Second)
timer.Stop()
}(i)
}
Sleep(3 * Second)
}
func TestSleepZeroDeadlock(t *testing.T) {
// Sleep(0) used to hang, the sequence of events was as follows.
// Sleep(0) sets G's status to Gwaiting, but then immediately returns leaving the status.
// Then the goroutine calls e.g. new and falls down into the scheduler due to pending GC.
// After the GC nobody wakes up the goroutine from Gwaiting status.
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
c := make(chan bool)
go func() {
for i := 0; i < 100; i++ {
runtime.GC()
}
c <- true
}()
for i := 0; i < 100; i++ {
Sleep(0)
tmp := make(chan bool, 1)
tmp <- true
<-tmp
}
<-c
}
func testReset(d Duration) error {
t0 := NewTimer(2 * d)
Sleep(d)
if !t0.Reset(3 * d) {
return errors.New("resetting unfired timer returned false")
}
Sleep(2 * d)
select {
case <-t0.C:
return errors.New("timer fired early")
default:
}
Sleep(2 * d)
select {
case <-t0.C:
default:
return errors.New("reset timer did not fire")
}
if t0.Reset(50 * Millisecond) {
return errors.New("resetting expired timer returned true")
}
return nil
}
func TestReset(t *testing.T) {
// We try to run this test with increasingly larger multiples
// until one works so slow, loaded hardware isn't as flaky,
// but without slowing down fast machines unnecessarily.
const unit = 25 * Millisecond
tries := []Duration{
1 * unit,
3 * unit,
7 * unit,
15 * unit,
}
var err error
for _, d := range tries {
err = testReset(d)
if err == nil {
t.Logf("passed using duration %v", d)
return
}
}
t.Error(err)
}
// Test that sleeping (via Sleep or Timer) for an interval so large it
// overflows does not result in a short sleep duration. Nor does it interfere
// with execution of other timers. If it does, timers in this or subsequent
// tests may not fire.
func TestOverflowSleep(t *testing.T) {
const big = Duration(int64(1<<63 - 1))
go func() {
Sleep(big)
// On failure, this may return after the test has completed, so
// we need to panic instead.
panic("big sleep returned")
}()
select {
case <-After(big):
t.Fatalf("big timeout fired")
case <-After(25 * Millisecond):
// OK
}
const neg = Duration(-1 << 63)
Sleep(neg) // Returns immediately.
select {
case <-After(neg):
// OK
case <-After(1 * Second):
t.Fatalf("negative timeout didn't fire")
}
}
// Test that a panic while deleting a timer does not leave
// the timers mutex held, deadlocking a ticker.Stop in a defer.
func TestIssue5745(t *testing.T) {
ticker := NewTicker(Hour)
defer func() {
// would deadlock here before the fix due to
// lock taken before the segfault.
ticker.Stop()
if r := recover(); r == nil {
t.Error("Expected panic, but none happened.")
}
}()
// cause a panic due to a segfault
var timer *Timer
timer.Stop()
t.Error("Should be unreachable.")
}
func TestOverflowPeriodRuntimeTimer(t *testing.T) {
// This may hang forever if timers are broken. See comment near
// the end of CheckRuntimeTimerOverflow in internal_test.go.
CheckRuntimeTimerPeriodOverflow()
}
func checkZeroPanicString(t *testing.T) {
e := recover()
s, _ := e.(string)
if want := "called on uninitialized Timer"; !strings.Contains(s, want) {
t.Errorf("panic = %v; want substring %q", e, want)
}
}
func TestZeroTimerResetPanics(t *testing.T) {
defer checkZeroPanicString(t)
var tr Timer
tr.Reset(1)
}
func TestZeroTimerStopPanics(t *testing.T) {
defer checkZeroPanicString(t)
var tr Timer
tr.Stop()
}
// Test that zero duration timers aren't missed by the scheduler. Regression test for issue 44868.
func TestZeroTimer(t *testing.T) {
if testing.Short() {
t.Skip("-short")
}
for i := 0; i < 1000000; i++ {
s := Now()
ti := NewTimer(0)
<-ti.C
if diff := Since(s); diff > 2*Second {
t.Errorf("Expected time to get value from Timer channel in less than 2 sec, took %v", diff)
}
}
}
// Test that rapidly moving a timer earlier doesn't cause it to get dropped.
// Issue 47329.
func TestTimerModifiedEarlier(t *testing.T) {
past := Until(Unix(0, 0))
count := 1000
fail := 0
for i := 0; i < count; i++ {
timer := NewTimer(Hour)
for j := 0; j < 10; j++ {
if !timer.Stop() {
<-timer.C
}
timer.Reset(past)
}
deadline := NewTimer(10 * Second)
defer deadline.Stop()
now := Now()
select {
case <-timer.C:
if since := Since(now); since > 8*Second {
t.Errorf("timer took too long (%v)", since)
fail++
}
case <-deadline.C:
t.Error("deadline expired")
}
}
if fail > 0 {
t.Errorf("%d failures", fail)
}
}
// Test that rapidly moving timers earlier and later doesn't cause
// some of the sleep times to be lost.
// Issue 47762
func TestAdjustTimers(t *testing.T) {
var rnd = rand.New(rand.NewSource(Now().UnixNano()))
timers := make([]*Timer, 100)
states := make([]int, len(timers))
indices := rnd.Perm(len(timers))
for len(indices) != 0 {
var ii = rnd.Intn(len(indices))
var i = indices[ii]
var timer = timers[i]
var state = states[i]
states[i]++
switch state {
case 0:
timers[i] = NewTimer(0)
case 1:
<-timer.C // Timer is now idle.
// Reset to various long durations, which we'll cancel.
case 2:
if timer.Reset(1 * Minute) {
panic("shouldn't be active (1)")
}
case 4:
if timer.Reset(3 * Minute) {
panic("shouldn't be active (3)")
}
case 6:
if timer.Reset(2 * Minute) {
panic("shouldn't be active (2)")
}
// Stop and drain a long-duration timer.
case 3, 5, 7:
if !timer.Stop() {
t.Logf("timer %d state %d Stop returned false", i, state)
<-timer.C
}
// Start a short-duration timer we expect to select without blocking.
case 8:
if timer.Reset(0) {
t.Fatal("timer.Reset returned true")
}
case 9:
now := Now()
<-timer.C
dur := Since(now)
if dur > 750*Millisecond {
t.Errorf("timer %d took %v to complete", i, dur)
}
// Timer is done. Swap with tail and remove.
case 10:
indices[ii] = indices[len(indices)-1]
indices = indices[:len(indices)-1]
}
}
}
// Benchmark timer latency when the thread that creates the timer is busy with
// other work and the timers must be serviced by other threads.
// https://golang.org/issue/38860
func BenchmarkParallelTimerLatency(b *testing.B) {
gmp := runtime.GOMAXPROCS(0)
if gmp < 2 || runtime.NumCPU() < gmp {
b.Skip("skipping with GOMAXPROCS < 2 or NumCPU < GOMAXPROCS")
}
// allocate memory now to avoid GC interference later.
timerCount := gmp - 1
stats := make([]struct {
sum float64
max Duration
count int64
_ [5]int64 // cache line padding
}, timerCount)
// Ensure the time to start new threads to service timers will not pollute
// the results.
warmupScheduler(gmp)
// Note that other than the AfterFunc calls this benchmark is measuring it
// avoids using any other timers. In particular, the main goroutine uses
// doWork to spin for some durations because up through Go 1.15 if all
// threads are idle sysmon could leave deep sleep when we wake.
// Ensure sysmon is in deep sleep.
doWork(30 * Millisecond)
b.ResetTimer()
const delay = Millisecond
var wg sync.WaitGroup
var count int32
for i := 0; i < b.N; i++ {
wg.Add(timerCount)
atomic.StoreInt32(&count, 0)
for j := 0; j < timerCount; j++ {
j := j
expectedWakeup := Now().Add(delay)
AfterFunc(delay, func() {
late := Since(expectedWakeup)
if late < 0 {
late = 0
}
stats[j].count++
stats[j].sum += float64(late.Nanoseconds())
if late > stats[j].max {
stats[j].max = late
}
atomic.AddInt32(&count, 1)
for atomic.LoadInt32(&count) < int32(timerCount) {
// spin until all timers fired
}
wg.Done()
})
}
for atomic.LoadInt32(&count) < int32(timerCount) {
// spin until all timers fired
}
wg.Wait()
// Spin for a bit to let the other scheduler threads go idle before the
// next round.
doWork(Millisecond)
}
var total float64
var samples float64
max := Duration(0)
for _, s := range stats {
if s.max > max {
max = s.max
}
total += s.sum
samples += float64(s.count)
}
b.ReportMetric(0, "ns/op")
b.ReportMetric(total/samples, "avg-late-ns")
b.ReportMetric(float64(max.Nanoseconds()), "max-late-ns")
}
// Benchmark timer latency with staggered wakeup times and varying CPU bound
// workloads. https://golang.org/issue/38860
func BenchmarkStaggeredTickerLatency(b *testing.B) {
gmp := runtime.GOMAXPROCS(0)
if gmp < 2 || runtime.NumCPU() < gmp {
b.Skip("skipping with GOMAXPROCS < 2 or NumCPU < GOMAXPROCS")
}
const delay = 3 * Millisecond
for _, dur := range []Duration{300 * Microsecond, 2 * Millisecond} {
b.Run(fmt.Sprintf("work-dur=%s", dur), func(b *testing.B) {
for tickersPerP := 1; tickersPerP < int(delay/dur)+1; tickersPerP++ {
tickerCount := gmp * tickersPerP
b.Run(fmt.Sprintf("tickers-per-P=%d", tickersPerP), func(b *testing.B) {
// allocate memory now to avoid GC interference later.
stats := make([]struct {
sum float64
max Duration
count int64
_ [5]int64 // cache line padding
}, tickerCount)
// Ensure the time to start new threads to service timers
// will not pollute the results.
warmupScheduler(gmp)
b.ResetTimer()
var wg sync.WaitGroup
wg.Add(tickerCount)
for j := 0; j < tickerCount; j++ {
j := j
doWork(delay / Duration(gmp))
expectedWakeup := Now().Add(delay)
ticker := NewTicker(delay)
go func(c int, ticker *Ticker, firstWake Time) {
defer ticker.Stop()
for ; c > 0; c-- {
<-ticker.C
late := Since(expectedWakeup)
if late < 0 {
late = 0
}
stats[j].count++
stats[j].sum += float64(late.Nanoseconds())
if late > stats[j].max {
stats[j].max = late
}
expectedWakeup = expectedWakeup.Add(delay)
doWork(dur)
}
wg.Done()
}(b.N, ticker, expectedWakeup)
}
wg.Wait()
var total float64
var samples float64
max := Duration(0)
for _, s := range stats {
if s.max > max {
max = s.max
}
total += s.sum
samples += float64(s.count)
}
b.ReportMetric(0, "ns/op")
b.ReportMetric(total/samples, "avg-late-ns")
b.ReportMetric(float64(max.Nanoseconds()), "max-late-ns")
})
}
})
}
}
// warmupScheduler ensures the scheduler has at least targetThreadCount threads
// in its thread pool.
func warmupScheduler(targetThreadCount int) {
var wg sync.WaitGroup
var count int32
for i := 0; i < targetThreadCount; i++ {
wg.Add(1)
go func() {
atomic.AddInt32(&count, 1)
for atomic.LoadInt32(&count) < int32(targetThreadCount) {
// spin until all threads started
}
// spin a bit more to ensure they are all running on separate CPUs.
doWork(Millisecond)
wg.Done()
}()
}
wg.Wait()
}
func doWork(dur Duration) {
start := Now()
for Since(start) < dur {
}
}
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