func benchmarkSyscall(b *testing.B, work, excess int) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1) * excess
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
for p := 0; p < procs; p++ {
go func() {
foo := 42
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
runtime.Entersyscall()
for i := 0; i < work; i++ {
foo *= 2
foo /= 2
}
runtime.Exitsyscall()
}
}
c <- foo == 42
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func TestFutexsleep(t *testing.T) {
if runtime.GOMAXPROCS(0) > 1 {
// futexsleep doesn't handle EINTR or other signals,
// so spurious wakeups may happen.
t.Skip("skipping; GOMAXPROCS>1")
}
start := time.Now()
var wg sync.WaitGroup
for i := range futexsleepTests {
tt := &futexsleepTests[i]
tt.mtx = 0
tt.ch = make(chan *futexsleepTest, 1)
wg.Add(1)
go func(tt *futexsleepTest) {
runtime.Entersyscall(0)
runtime.Futexsleep(&tt.mtx, 0, tt.ns)
runtime.Exitsyscall(0)
tt.ch <- tt
wg.Done()
}(tt)
}
loop:
for {
select {
case tt := <-futexsleepTests[beforeY2038].ch:
t.Errorf("futexsleep test %q finished early after %s", tt.msg, time.Since(start))
break loop
case tt := <-futexsleepTests[afterY2038].ch:
// Looks like FreeBSD 10 kernel has changed
// the semantics of timedwait on userspace
// mutex to make broken stuff look broken.
switch {
case runtime.GOOS == "freebsd" && runtime.GOARCH == "386":
t.Log("freebsd/386 may not work correctly after the year 2038, see golang.org/issue/7194")
default:
t.Errorf("futexsleep test %q finished early after %s", tt.msg, time.Since(start))
break loop
}
case <-time.After(time.Second):
break loop
}
}
for i := range futexsleepTests {
tt := &futexsleepTests[i]
atomic.StoreUint32(&tt.mtx, 1)
runtime.Futexwakeup(&tt.mtx, 1)
}
wg.Wait()
}
func benchmarkSyscall(b *testing.B, work, excess int) {
b.SetParallelism(excess)
b.RunParallel(func(pb *testing.PB) {
foo := 42
for pb.Next() {
runtime.Entersyscall(0)
for i := 0; i < work; i++ {
foo *= 2
foo /= 2
}
runtime.Exitsyscall(0)
}
_ = foo
})
}
func BenchmarkSyscall(b *testing.B) {
const CallsPerSched = 1000
procs := runtime.GOMAXPROCS(-1)
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
for p := 0; p < procs; p++ {
go func() {
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
runtime.Entersyscall()
runtime.Exitsyscall()
}
}
c <- true
}()
}
for p := 0; p < procs; p++ {
<-c
}
}