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// 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.
// GOMAXPROCS=10 go test
package sync_test
import (
"runtime"
. "sync"
"sync/atomic"
"testing"
)
func HammerSemaphore(s *uint32, loops int, cdone chan bool) {
for i := 0; i < loops; i++ {
Runtime_Semacquire(s)
Runtime_Semrelease(s)
}
cdone <- true
}
func TestSemaphore(t *testing.T) {
s := new(uint32)
*s = 1
c := make(chan bool)
for i := 0; i < 10; i++ {
go HammerSemaphore(s, 1000, c)
}
for i := 0; i < 10; i++ {
<-c
}
}
func BenchmarkUncontendedSemaphore(b *testing.B) {
s := new(uint32)
*s = 1
HammerSemaphore(s, b.N, make(chan bool, 2))
}
func BenchmarkContendedSemaphore(b *testing.B) {
b.StopTimer()
s := new(uint32)
*s = 1
c := make(chan bool)
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
b.StartTimer()
go HammerSemaphore(s, b.N/2, c)
go HammerSemaphore(s, b.N/2, c)
<-c
<-c
}
func HammerMutex(m *Mutex, loops int, cdone chan bool) {
for i := 0; i < loops; i++ {
m.Lock()
m.Unlock()
}
cdone <- true
}
func TestMutex(t *testing.T) {
m := new(Mutex)
c := make(chan bool)
for i := 0; i < 10; i++ {
go HammerMutex(m, 1000, c)
}
for i := 0; i < 10; i++ {
<-c
}
}
func TestMutexPanic(t *testing.T) {
defer func() {
if recover() == nil {
t.Fatalf("unlock of unlocked mutex did not panic")
}
}()
var mu Mutex
mu.Lock()
mu.Unlock()
mu.Unlock()
}
func BenchmarkMutexUncontended(b *testing.B) {
type PaddedMutex struct {
Mutex
pad [128]uint8
}
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() {
var mu PaddedMutex
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
mu.Lock()
mu.Unlock()
}
}
c <- true
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func benchmarkMutex(b *testing.B, slack, work bool) {
const (
CallsPerSched = 1000
LocalWork = 100
GoroutineSlack = 10
)
procs := runtime.GOMAXPROCS(-1)
if slack {
procs *= GoroutineSlack
}
N := int32(b.N / CallsPerSched)
c := make(chan bool, procs)
var mu Mutex
for p := 0; p < procs; p++ {
go func() {
foo := 0
for atomic.AddInt32(&N, -1) >= 0 {
runtime.Gosched()
for g := 0; g < CallsPerSched; g++ {
mu.Lock()
mu.Unlock()
if work {
for i := 0; i < LocalWork; i++ {
foo *= 2
foo /= 2
}
}
}
}
c <- foo == 42
}()
}
for p := 0; p < procs; p++ {
<-c
}
}
func BenchmarkMutex(b *testing.B) {
benchmarkMutex(b, false, false)
}
func BenchmarkMutexSlack(b *testing.B) {
benchmarkMutex(b, true, false)
}
func BenchmarkMutexWork(b *testing.B) {
benchmarkMutex(b, false, true)
}
func BenchmarkMutexWorkSlack(b *testing.B) {
benchmarkMutex(b, true, true)
}
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