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|
package stm
import (
"sync"
"testing"
"time"
)
func TestDecrement(t *testing.T) {
x := NewVar(1000)
for i := 0; i < 500; i++ {
go Atomically(func(tx *Tx) {
cur := tx.Get(x).(int)
tx.Set(x, cur-1)
})
}
done := make(chan struct{})
go func() {
for {
if AtomicGet(x).(int) == 500 {
break
}
}
done <- struct{}{}
}()
select {
case <-done:
case <-time.After(time.Second):
t.Fatal("decrement did not complete in time")
}
}
// read-only transaction aren't exempt from calling tx.verify
func TestReadVerify(t *testing.T) {
read := make(chan struct{})
x, y := NewVar(1), NewVar(2)
// spawn a transaction that writes to x
go func() {
<-read
AtomicSet(x, 3)
read <- struct{}{}
// other tx should retry, so we need to read/send again
read <- <-read
}()
// spawn a transaction that reads x, then y. The other tx will modify x in
// between the reads, causing this tx to retry.
var x2, y2 int
Atomically(func(tx *Tx) {
x2 = tx.Get(x).(int)
read <- struct{}{}
<-read // wait for other tx to complete
y2 = tx.Get(y).(int)
})
if x2 == 1 && y2 == 2 {
t.Fatal("read was not verified")
}
}
func TestRetry(t *testing.T) {
x := NewVar(10)
// spawn 10 transactions, one every 10 milliseconds. This will decrement x
// to 0 over the course of 100 milliseconds.
go func() {
for i := 0; i < 10; i++ {
time.Sleep(10 * time.Millisecond)
Atomically(func(tx *Tx) {
cur := tx.Get(x).(int)
tx.Set(x, cur-1)
})
}
}()
// Each time we read x before the above loop has finished, we need to
// retry. This should result in no more than 1 retry per transaction.
retry := 0
Atomically(func(tx *Tx) {
cur := tx.Get(x).(int)
if cur != 0 {
retry++
tx.Retry()
}
})
if retry > 10 {
t.Fatal("should have retried at most 10 times, got", retry)
}
}
func TestVerify(t *testing.T) {
// tx.verify should check more than pointer equality
type foo struct {
i int
}
x := NewVar(&foo{3})
read := make(chan struct{})
// spawn a transaction that modifies x
go func() {
Atomically(func(tx *Tx) {
<-read
rx := tx.Get(x).(*foo)
rx.i = 7
tx.Set(x, rx)
})
read <- struct{}{}
// other tx should retry, so we need to read/send again
read <- <-read
}()
// spawn a transaction that reads x, then y. The other tx will modify x in
// between the reads, causing this tx to retry.
var i int
Atomically(func(tx *Tx) {
f := tx.Get(x).(*foo)
i = f.i
read <- struct{}{}
<-read // wait for other tx to complete
})
if i == 3 {
t.Fatal("verify did not retry despite modified Var", i)
}
}
func TestSelect(t *testing.T) {
// empty Select should block forever
c := make(chan struct{})
go func() {
Atomically(Select())
c <- struct{}{}
}()
select {
case <-c:
t.Fatal("empty Select did not block forever")
case <-time.After(10*time.Millisecond):
}
// with one arg, Select adds no effect
x := NewVar(2)
Atomically(Select(func(tx *Tx) {
tx.Assert(tx.Get(x).(int) == 2)
}))
var picked int
Atomically(Select(
// always blocks; should never be selected
func(tx *Tx) {
tx.Retry()
picked = 1
},
// always succeeds; should always be selected
func(tx *Tx) {
picked = 2
},
// always succeeds; should never be selected
func(tx *Tx) {
picked = 3
},
))
if picked != 2 {
t.Fatal("Select selected wrong transaction:", picked)
}
}
func TestCompose(t *testing.T) {
nums := make([]int, 100)
fns := make([]func(*Tx), 100)
for i := range fns {
fns[i] = func(x int) func(*Tx) {
return func(*Tx) { nums[x] = x }
}(i) // capture loop var
}
Atomically(Compose(fns...))
for i := range nums {
if nums[i] != i {
t.Error("Compose failed:", nums[i], i)
}
}
}
func BenchmarkAtomicGet(b *testing.B) {
x := NewVar(0)
for i := 0; i < b.N; i++ {
AtomicGet(x)
}
}
func BenchmarkAtomicSet(b *testing.B) {
x := NewVar(0)
for i := 0; i < b.N; i++ {
AtomicSet(x, 0)
}
}
func BenchmarkIncrementSTM(b *testing.B) {
for i := 0; i < b.N; i++ {
// spawn 1000 goroutines that each increment x by 1
x := NewVar(0)
for i := 0; i < 1000; i++ {
go Atomically(func(tx *Tx) {
cur := tx.Get(x).(int)
tx.Set(x, cur+1)
})
}
// wait for x to reach 1000
Atomically(func(tx *Tx) {
tx.Assert(tx.Get(x).(int) == 1000)
})
}
}
func BenchmarkIncrementMutex(b *testing.B) {
for i := 0; i < b.N; i++ {
var mu sync.Mutex
x := 0
for i := 0; i < 1000; i++ {
go func() {
mu.Lock()
x++
mu.Unlock()
}()
}
for {
mu.Lock()
read := x
mu.Unlock()
if read == 1000 {
break
}
}
}
}
func BenchmarkIncrementChannel(b *testing.B) {
for i := 0; i < b.N; i++ {
c := make(chan int, 1)
c <- 0
for i := 0; i < 1000; i++ {
go func() {
c <- 1 + <-c
}()
}
for {
read := <-c
if read == 1000 {
break
}
c <- read
}
}
}
func BenchmarkReadVarSTM(b *testing.B) {
for i := 0; i < b.N; i++ {
var wg sync.WaitGroup
wg.Add(1000)
x := NewVar(0)
for i := 0; i < 1000; i++ {
go func() {
AtomicGet(x)
wg.Done()
}()
}
wg.Wait()
}
}
func BenchmarkReadVarMutex(b *testing.B) {
for i := 0; i < b.N; i++ {
var mu sync.Mutex
var wg sync.WaitGroup
wg.Add(1000)
x := 0
for i := 0; i < 1000; i++ {
go func() {
mu.Lock()
_ = x
mu.Unlock()
wg.Done()
}()
}
wg.Wait()
}
}
func BenchmarkReadVarChannel(b *testing.B) {
for i := 0; i < b.N; i++ {
var wg sync.WaitGroup
wg.Add(1000)
c := make(chan int)
close(c)
for i := 0; i < 1000; i++ {
go func() {
<-c
wg.Done()
}()
}
wg.Wait()
}
}
|
