// Copyright 2011 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 runtime_test
import (
"fmt"
"math"
"net"
"runtime"
"runtime/debug"
"strings"
"sync"
"sync/atomic"
"syscall"
"testing"
"time"
)
var stop = make(chan bool, 1)
func perpetuumMobile() {
select {
case <-stop:
default:
go perpetuumMobile()
}
}
func TestStopTheWorldDeadlock(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
if testing.Short() {
t.Skip("skipping during short test")
}
maxprocs := runtime.GOMAXPROCS(3)
compl := make(chan bool, 2)
go func() {
for i := 0; i != 1000; i += 1 {
runtime.GC()
}
compl <- true
}()
go func() {
for i := 0; i != 1000; i += 1 {
runtime.GOMAXPROCS(3)
}
compl <- true
}()
go perpetuumMobile()
<-compl
<-compl
stop <- true
runtime.GOMAXPROCS(maxprocs)
}
func TestYieldProgress(t *testing.T) {
testYieldProgress(false)
}
func TestYieldLockedProgress(t *testing.T) {
testYieldProgress(true)
}
func testYieldProgress(locked bool) {
c := make(chan bool)
cack := make(chan bool)
go func() {
if locked {
runtime.LockOSThread()
}
for {
select {
case <-c:
cack <- true
return
default:
runtime.Gosched()
}
}
}()
time.Sleep(10 * time.Millisecond)
c <- true
<-cack
}
func TestYieldLocked(t *testing.T) {
const N = 10
c := make(chan bool)
go func() {
runtime.LockOSThread()
for i := 0; i < N; i++ {
runtime.Gosched()
time.Sleep(time.Millisecond)
}
c <- true
// runtime.UnlockOSThread() is deliberately omitted
}()
<-c
}
func TestGoroutineParallelism(t *testing.T) {
if runtime.NumCPU() == 1 {
// Takes too long, too easy to deadlock, etc.
t.Skip("skipping on uniprocessor")
}
P := 4
N := 10
if testing.Short() {
P = 3
N = 3
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(P))
// If runtime triggers a forced GC during this test then it will deadlock,
// since the goroutines can't be stopped/preempted.
// Disable GC for this test (see issue #10958).
defer debug.SetGCPercent(debug.SetGCPercent(-1))
for try := 0; try < N; try++ {
done := make(chan bool)
x := uint32(0)
for p := 0; p < P; p++ {
// Test that all P goroutines are scheduled at the same time
go func(p int) {
for i := 0; i < 3; i++ {
expected := uint32(P*i + p)
for atomic.LoadUint32(&x) != expected {
}
atomic.StoreUint32(&x, expected+1)
}
done <- true
}(p)
}
for p := 0; p < P; p++ {
<-done
}
}
}
// Test that all runnable goroutines are scheduled at the same time.
func TestGoroutineParallelism2(t *testing.T) {
//testGoroutineParallelism2(t, false, false)
testGoroutineParallelism2(t, true, false)
testGoroutineParallelism2(t, false, true)
testGoroutineParallelism2(t, true, true)
}
func testGoroutineParallelism2(t *testing.T, load, netpoll bool) {
if runtime.NumCPU() == 1 {
// Takes too long, too easy to deadlock, etc.
t.Skip("skipping on uniprocessor")
}
P := 4
N := 10
if testing.Short() {
N = 3
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(P))
// If runtime triggers a forced GC during this test then it will deadlock,
// since the goroutines can't be stopped/preempted.
// Disable GC for this test (see issue #10958).
defer debug.SetGCPercent(debug.SetGCPercent(-1))
for try := 0; try < N; try++ {
if load {
// Create P goroutines and wait until they all run.
// When we run the actual test below, worker threads
// running the goroutines will start parking.
done := make(chan bool)
x := uint32(0)
for p := 0; p < P; p++ {
go func() {
if atomic.AddUint32(&x, 1) == uint32(P) {
done <- true
return
}
for atomic.LoadUint32(&x) != uint32(P) {
}
}()
}
<-done
}
if netpoll {
// Enable netpoller, affects schedler behavior.
laddr := "localhost:0"
if runtime.GOOS == "android" {
// On some Android devices, there are no records for localhost,
// see https://golang.org/issues/14486.
// Don't use 127.0.0.1 for every case, it won't work on IPv6-only systems.
laddr = "127.0.0.1:0"
}
ln, err := net.Listen("tcp", laddr)
if err != nil {
defer ln.Close() // yup, defer in a loop
}
}
done := make(chan bool)
x := uint32(0)
// Spawn P goroutines in a nested fashion just to differ from TestGoroutineParallelism.
for p := 0; p < P/2; p++ {
go func(p int) {
for p2 := 0; p2 < 2; p2++ {
go func(p2 int) {
for i := 0; i < 3; i++ {
expected := uint32(P*i + p*2 + p2)
for atomic.LoadUint32(&x) != expected {
}
atomic.StoreUint32(&x, expected+1)
}
done <- true
}(p2)
}
}(p)
}
for p := 0; p < P; p++ {
<-done
}
}
}
func TestBlockLocked(t *testing.T) {
const N = 10
c := make(chan bool)
go func() {
runtime.LockOSThread()
for i := 0; i < N; i++ {
c <- true
}
runtime.UnlockOSThread()
}()
for i := 0; i < N; i++ {
<-c
}
}
func TestTimerFairness(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
done := make(chan bool)
c := make(chan bool)
for i := 0; i < 2; i++ {
go func() {
for {
select {
case c <- true:
case <-done:
return
}
}
}()
}
timer := time.After(20 * time.Millisecond)
for {
select {
case <-c:
case <-timer:
close(done)
return
}
}
}
func TestTimerFairness2(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
done := make(chan bool)
c := make(chan bool)
for i := 0; i < 2; i++ {
go func() {
timer := time.After(20 * time.Millisecond)
var buf [1]byte
for {
syscall.Read(0, buf[0:0])
select {
case c <- true:
case <-c:
case <-timer:
done <- true
return
}
}
}()
}
<-done
<-done
}
// The function is used to test preemption at split stack checks.
// Declaring a var avoids inlining at the call site.
var preempt = func() int {
var a [128]int
sum := 0
for _, v := range a {
sum += v
}
return sum
}
func TestPreemption(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
// Test that goroutines are preempted at function calls.
N := 5
if testing.Short() {
N = 2
}
c := make(chan bool)
var x uint32
for g := 0; g < 2; g++ {
go func(g int) {
for i := 0; i < N; i++ {
for atomic.LoadUint32(&x) != uint32(g) {
preempt()
}
atomic.StoreUint32(&x, uint32(1-g))
}
c <- true
}(g)
}
<-c
<-c
}
func TestPreemptionGC(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
// Test that pending GC preempts running goroutines.
P := 5
N := 10
if testing.Short() {
P = 3
N = 2
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(P + 1))
var stop uint32
for i := 0; i < P; i++ {
go func() {
for atomic.LoadUint32(&stop) == 0 {
preempt()
}
}()
}
for i := 0; i < N; i++ {
runtime.Gosched()
runtime.GC()
}
atomic.StoreUint32(&stop, 1)
}
func TestGCFairness(t *testing.T) {
output := runTestProg(t, "testprog", "GCFairness")
want := "OK\n"
if output != want {
t.Fatalf("want %s, got %s\n", want, output)
}
}
func TestGCFairness2(t *testing.T) {
output := runTestProg(t, "testprog", "GCFairness2")
want := "OK\n"
if output != want {
t.Fatalf("want %s, got %s\n", want, output)
}
}
func TestNumGoroutine(t *testing.T) {
output := runTestProg(t, "testprog", "NumGoroutine")
want := "1\n"
if output != want {
t.Fatalf("want %q, got %q", want, output)
}
buf := make([]byte, 1<<20)
// Try up to 10 times for a match before giving up.
// This is a fundamentally racy check but it's important
// to notice if NumGoroutine and Stack are _always_ out of sync.
for i := 0; ; i++ {
// Give goroutines about to exit a chance to exit.
// The NumGoroutine and Stack below need to see
// the same state of the world, so anything we can do
// to keep it quiet is good.
runtime.Gosched()
n := runtime.NumGoroutine()
buf = buf[:runtime.Stack(buf, true)]
nstk := strings.Count(string(buf), "goroutine ")
if n == nstk {
break
}
if i >= 10 {
t.Fatalf("NumGoroutine=%d, but found %d goroutines in stack dump: %s", n, nstk, buf)
}
}
}
func TestPingPongHog(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
if testing.Short() {
t.Skip("skipping in -short mode")
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
done := make(chan bool)
hogChan, lightChan := make(chan bool), make(chan bool)
hogCount, lightCount := 0, 0
run := func(limit int, counter *int, wake chan bool) {
for {
select {
case <-done:
return
case <-wake:
for i := 0; i < limit; i++ {
*counter++
}
wake <- true
}
}
}
// Start two co-scheduled hog goroutines.
for i := 0; i < 2; i++ {
go run(1e6, &hogCount, hogChan)
}
// Start two co-scheduled light goroutines.
for i := 0; i < 2; i++ {
go run(1e3, &lightCount, lightChan)
}
// Start goroutine pairs and wait for a few preemption rounds.
hogChan <- true
lightChan <- true
time.Sleep(100 * time.Millisecond)
close(done)
<-hogChan
<-lightChan
// Check that hogCount and lightCount are within a factor of
// 5, which indicates that both pairs of goroutines handed off
// the P within a time-slice to their buddy. We can use a
// fairly large factor here to make this robust: if the
// scheduler isn't working right, the gap should be ~1000X.
const factor = 5
if hogCount > lightCount*factor || lightCount > hogCount*factor {
t.Fatalf("want hogCount/lightCount in [%v, %v]; got %d/%d = %g", 1.0/factor, factor, hogCount, lightCount, float64(hogCount)/float64(lightCount))
}
}
func BenchmarkPingPongHog(b *testing.B) {
if b.N == 0 {
return
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
// Create a CPU hog
stop, done := make(chan bool), make(chan bool)
go func() {
for {
select {
case <-stop:
done <- true
return
default:
}
}
}()
// Ping-pong b.N times
ping, pong := make(chan bool), make(chan bool)
go func() {
for j := 0; j < b.N; j++ {
pong <- <-ping
}
close(stop)
done <- true
}()
go func() {
for i := 0; i < b.N; i++ {
ping <- <-pong
}
done <- true
}()
b.ResetTimer()
ping <- true // Start ping-pong
<-stop
b.StopTimer()
<-ping // Let last ponger exit
<-done // Make sure goroutines exit
<-done
<-done
}
func stackGrowthRecursive(i int) {
var pad [128]uint64
if i != 0 && pad[0] == 0 {
stackGrowthRecursive(i - 1)
}
}
func TestPreemptSplitBig(t *testing.T) {
if testing.Short() {
t.Skip("skipping in -short mode")
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
stop := make(chan int)
go big(stop)
for i := 0; i < 3; i++ {
time.Sleep(10 * time.Microsecond) // let big start running
runtime.GC()
}
close(stop)
}
func big(stop chan int) int {
n := 0
for {
// delay so that gc is sure to have asked for a preemption
for i := 0; i < 1e9; i++ {
n++
}
// call bigframe, which used to miss the preemption in its prologue.
bigframe(stop)
// check if we've been asked to stop.
select {
case <-stop:
return n
}
}
}
func bigframe(stop chan int) int {
// not splitting the stack will overflow.
// small will notice that it needs a stack split and will
// catch the overflow.
var x [8192]byte
return small(stop, &x)
}
func small(stop chan int, x *[8192]byte) int {
for i := range x {
x[i] = byte(i)
}
sum := 0
for i := range x {
sum += int(x[i])
}
// keep small from being a leaf function, which might
// make it not do any stack check at all.
nonleaf(stop)
return sum
}
func nonleaf(stop chan int) bool {
// do something that won't be inlined:
select {
case <-stop:
return true
default:
return false
}
}
func TestSchedLocalQueue(t *testing.T) {
runtime.RunSchedLocalQueueTest()
}
func TestSchedLocalQueueSteal(t *testing.T) {
runtime.RunSchedLocalQueueStealTest()
}
func TestSchedLocalQueueEmpty(t *testing.T) {
if runtime.NumCPU() == 1 {
// Takes too long and does not trigger the race.
t.Skip("skipping on uniprocessor")
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
// If runtime triggers a forced GC during this test then it will deadlock,
// since the goroutines can't be stopped/preempted during spin wait.
defer debug.SetGCPercent(debug.SetGCPercent(-1))
iters := int(1e5)
if testing.Short() {
iters = 1e2
}
runtime.RunSchedLocalQueueEmptyTest(iters)
}
func benchmarkStackGrowth(b *testing.B, rec int) {
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
stackGrowthRecursive(rec)
}
})
}
func BenchmarkStackGrowth(b *testing.B) {
benchmarkStackGrowth(b, 10)
}
func BenchmarkStackGrowthDeep(b *testing.B) {
benchmarkStackGrowth(b, 1024)
}
func BenchmarkCreateGoroutines(b *testing.B) {
benchmarkCreateGoroutines(b, 1)
}
func BenchmarkCreateGoroutinesParallel(b *testing.B) {
benchmarkCreateGoroutines(b, runtime.GOMAXPROCS(-1))
}
func benchmarkCreateGoroutines(b *testing.B, procs int) {
c := make(chan bool)
var f func(n int)
f = func(n int) {
if n == 0 {
c <- true
return
}
go f(n - 1)
}
for i := 0; i < procs; i++ {
go f(b.N / procs)
}
for i := 0; i < procs; i++ {
<-c
}
}
func BenchmarkCreateGoroutinesCapture(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
const N = 4
var wg sync.WaitGroup
wg.Add(N)
for i := 0; i < N; i++ {
i := i
go func() {
if i >= N {
b.Logf("bad") // just to capture b
}
wg.Done()
}()
}
wg.Wait()
}
}
func BenchmarkClosureCall(b *testing.B) {
sum := 0
off1 := 1
for i := 0; i < b.N; i++ {
off2 := 2
func() {
sum += i + off1 + off2
}()
}
_ = sum
}
func benchmarkWakeupParallel(b *testing.B, spin func(time.Duration)) {
if runtime.GOMAXPROCS(0) == 1 {
b.Skip("skipping: GOMAXPROCS=1")
}
wakeDelay := 5 * time.Microsecond
for _, delay := range []time.Duration{
0,
1 * time.Microsecond,
2 * time.Microsecond,
5 * time.Microsecond,
10 * time.Microsecond,
20 * time.Microsecond,
50 * time.Microsecond,
100 * time.Microsecond,
} {
b.Run(delay.String(), func(b *testing.B) {
if b.N == 0 {
return
}
// Start two goroutines, which alternate between being
// sender and receiver in the following protocol:
//
// - The receiver spins for `delay` and then does a
// blocking receive on a channel.
//
// - The sender spins for `delay+wakeDelay` and then
// sends to the same channel. (The addition of
// `wakeDelay` improves the probability that the
// receiver will be blocking when the send occurs when
// the goroutines execute in parallel.)
//
// In each iteration of the benchmark, each goroutine
// acts once as sender and once as receiver, so each
// goroutine spins for delay twice.
//
// BenchmarkWakeupParallel is used to estimate how
// efficiently the scheduler parallelizes goroutines in
// the presence of blocking:
//
// - If both goroutines are executed on the same core,
// an increase in delay by N will increase the time per
// iteration by 4*N, because all 4 delays are
// serialized.
//
// - Otherwise, an increase in delay by N will increase
// the time per iteration by 2*N, and the time per
// iteration is 2 * (runtime overhead + chan
// send/receive pair + delay + wakeDelay). This allows
// the runtime overhead, including the time it takes
// for the unblocked goroutine to be scheduled, to be
// estimated.
ping, pong := make(chan struct{}), make(chan struct{})
start := make(chan struct{})
done := make(chan struct{})
go func() {
<-start
for i := 0; i < b.N; i++ {
// sender
spin(delay + wakeDelay)
ping <- struct{}{}
// receiver
spin(delay)
<-pong
}
done <- struct{}{}
}()
go func() {
for i := 0; i < b.N; i++ {
// receiver
spin(delay)
<-ping
// sender
spin(delay + wakeDelay)
pong <- struct{}{}
}
done <- struct{}{}
}()
b.ResetTimer()
start <- struct{}{}
<-done
<-done
})
}
}
func BenchmarkWakeupParallelSpinning(b *testing.B) {
benchmarkWakeupParallel(b, func(d time.Duration) {
end := time.Now().Add(d)
for time.Now().Before(end) {
// do nothing
}
})
}
// sysNanosleep is defined by OS-specific files (such as runtime_linux_test.go)
// to sleep for the given duration. If nil, dependent tests are skipped.
// The implementation should invoke a blocking system call and not
// call time.Sleep, which would deschedule the goroutine.
var sysNanosleep func(d time.Duration)
func BenchmarkWakeupParallelSyscall(b *testing.B) {
if sysNanosleep == nil {
b.Skipf("skipping on %v; sysNanosleep not defined", runtime.GOOS)
}
benchmarkWakeupParallel(b, func(d time.Duration) {
sysNanosleep(d)
})
}
type Matrix [][]float64
func BenchmarkMatmult(b *testing.B) {
b.StopTimer()
// matmult is O(N**3) but testing expects O(b.N),
// so we need to take cube root of b.N
n := int(math.Cbrt(float64(b.N))) + 1
A := makeMatrix(n)
B := makeMatrix(n)
C := makeMatrix(n)
b.StartTimer()
matmult(nil, A, B, C, 0, n, 0, n, 0, n, 8)
}
func makeMatrix(n int) Matrix {
m := make(Matrix, n)
for i := 0; i < n; i++ {
m[i] = make([]float64, n)
for j := 0; j < n; j++ {
m[i][j] = float64(i*n + j)
}
}
return m
}
func matmult(done chan<- struct{}, A, B, C Matrix, i0, i1, j0, j1, k0, k1, threshold int) {
di := i1 - i0
dj := j1 - j0
dk := k1 - k0
if di >= dj && di >= dk && di >= threshold {
// divide in two by y axis
mi := i0 + di/2
done1 := make(chan struct{}, 1)
go matmult(done1, A, B, C, i0, mi, j0, j1, k0, k1, threshold)
matmult(nil, A, B, C, mi, i1, j0, j1, k0, k1, threshold)
<-done1
} else if dj >= dk && dj >= threshold {
// divide in two by x axis
mj := j0 + dj/2
done1 := make(chan struct{}, 1)
go matmult(done1, A, B, C, i0, i1, j0, mj, k0, k1, threshold)
matmult(nil, A, B, C, i0, i1, mj, j1, k0, k1, threshold)
<-done1
} else if dk >= threshold {
// divide in two by "k" axis
// deliberately not parallel because of data races
mk := k0 + dk/2
matmult(nil, A, B, C, i0, i1, j0, j1, k0, mk, threshold)
matmult(nil, A, B, C, i0, i1, j0, j1, mk, k1, threshold)
} else {
// the matrices are small enough, compute directly
for i := i0; i < i1; i++ {
for j := j0; j < j1; j++ {
for k := k0; k < k1; k++ {
C[i][j] += A[i][k] * B[k][j]
}
}
}
}
if done != nil {
done <- struct{}{}
}
}
func TestStealOrder(t *testing.T) {
runtime.RunStealOrderTest()
}
func TestLockOSThreadNesting(t *testing.T) {
if runtime.GOARCH == "wasm" {
t.Skip("no threads on wasm yet")
}
go func() {
e, i := runtime.LockOSCounts()
if e != 0 || i != 0 {
t.Errorf("want locked counts 0, 0; got %d, %d", e, i)
return
}
runtime.LockOSThread()
runtime.LockOSThread()
runtime.UnlockOSThread()
e, i = runtime.LockOSCounts()
if e != 1 || i != 0 {
t.Errorf("want locked counts 1, 0; got %d, %d", e, i)
return
}
runtime.UnlockOSThread()
e, i = runtime.LockOSCounts()
if e != 0 || i != 0 {
t.Errorf("want locked counts 0, 0; got %d, %d", e, i)
return
}
}()
}
func TestLockOSThreadExit(t *testing.T) {
testLockOSThreadExit(t, "testprog")
}
func testLockOSThreadExit(t *testing.T, prog string) {
output := runTestProg(t, prog, "LockOSThreadMain", "GOMAXPROCS=1")
want := "OK\n"
if output != want {
t.Errorf("want %q, got %q", want, output)
}
output = runTestProg(t, prog, "LockOSThreadAlt")
if output != want {
t.Errorf("want %q, got %q", want, output)
}
}
func TestLockOSThreadAvoidsStatePropagation(t *testing.T) {
want := "OK\n"
skip := "unshare not permitted\n"
output := runTestProg(t, "testprog", "LockOSThreadAvoidsStatePropagation", "GOMAXPROCS=1")
if output == skip {
t.Skip("unshare syscall not permitted on this system")
} else if output != want {
t.Errorf("want %q, got %q", want, output)
}
}
// fakeSyscall emulates a system call.
//go:nosplit
func fakeSyscall(duration time.Duration) {
runtime.Entersyscall()
for start := runtime.Nanotime(); runtime.Nanotime()-start < int64(duration); {
}
runtime.Exitsyscall()
}
// Check that a goroutine will be preempted if it is calling short system calls.
func testPreemptionAfterSyscall(t *testing.T, syscallDuration time.Duration) {
if runtime.GOARCH == "wasm" {
t.Skip("no preemption on wasm yet")
}
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
interations := 10
if testing.Short() {
interations = 1
}
const (
maxDuration = 3 * time.Second
nroutines = 8
)
for i := 0; i < interations; i++ {
c := make(chan bool, nroutines)
stop := uint32(0)
start := time.Now()
for g := 0; g < nroutines; g++ {
go func(stop *uint32) {
c <- true
for atomic.LoadUint32(stop) == 0 {
fakeSyscall(syscallDuration)
}
c <- true
}(&stop)
}
// wait until all goroutines have started.
for g := 0; g < nroutines; g++ {
<-c
}
atomic.StoreUint32(&stop, 1)
// wait until all goroutines have finished.
for g := 0; g < nroutines; g++ {
<-c
}
duration := time.Since(start)
if duration > maxDuration {
t.Errorf("timeout exceeded: %v (%v)", duration, maxDuration)
}
}
}
func TestPreemptionAfterSyscall(t *testing.T) {
for _, i := range []time.Duration{10, 100, 1000} {
d := i * time.Microsecond
t.Run(fmt.Sprint(d), func(t *testing.T) {
testPreemptionAfterSyscall(t, d)
})
}
}
func TestGetgThreadSwitch(t *testing.T) {
runtime.RunGetgThreadSwitchTest()
}
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