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// Copyright 2022 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 (
"internal/goarch"
"internal/runtime/atomic"
"reflect"
. "runtime"
"runtime/debug"
"testing"
"time"
"unsafe"
)
type smallScalar struct {
X uintptr
}
type smallPointer struct {
X *smallPointer
}
type smallPointerMix struct {
A *smallPointer
B byte
C *smallPointer
D [11]byte
}
type mediumScalarEven [8192]byte
type mediumScalarOdd [3321]byte
type mediumPointerEven [1024]*smallPointer
type mediumPointerOdd [1023]*smallPointer
type largeScalar [UserArenaChunkBytes + 1]byte
type largePointer [UserArenaChunkBytes/unsafe.Sizeof(&smallPointer{}) + 1]*smallPointer
func TestUserArena(t *testing.T) {
// Set GOMAXPROCS to 2 so we don't run too many of these
// tests in parallel.
defer GOMAXPROCS(GOMAXPROCS(2))
// Start a subtest so that we can clean up after any parallel tests within.
t.Run("Alloc", func(t *testing.T) {
ss := &smallScalar{5}
runSubTestUserArenaNew(t, ss, true)
sp := &smallPointer{new(smallPointer)}
runSubTestUserArenaNew(t, sp, true)
spm := &smallPointerMix{sp, 5, nil, [11]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}}
runSubTestUserArenaNew(t, spm, true)
mse := new(mediumScalarEven)
for i := range mse {
mse[i] = 121
}
runSubTestUserArenaNew(t, mse, true)
mso := new(mediumScalarOdd)
for i := range mso {
mso[i] = 122
}
runSubTestUserArenaNew(t, mso, true)
mpe := new(mediumPointerEven)
for i := range mpe {
mpe[i] = sp
}
runSubTestUserArenaNew(t, mpe, true)
mpo := new(mediumPointerOdd)
for i := range mpo {
mpo[i] = sp
}
runSubTestUserArenaNew(t, mpo, true)
ls := new(largeScalar)
for i := range ls {
ls[i] = 123
}
// Not in parallel because we don't want to hold this large allocation live.
runSubTestUserArenaNew(t, ls, false)
lp := new(largePointer)
for i := range lp {
lp[i] = sp
}
// Not in parallel because we don't want to hold this large allocation live.
runSubTestUserArenaNew(t, lp, false)
sss := make([]smallScalar, 25)
for i := range sss {
sss[i] = smallScalar{12}
}
runSubTestUserArenaSlice(t, sss, true)
mpos := make([]mediumPointerOdd, 5)
for i := range mpos {
mpos[i] = *mpo
}
runSubTestUserArenaSlice(t, mpos, true)
sps := make([]smallPointer, UserArenaChunkBytes/unsafe.Sizeof(smallPointer{})+1)
for i := range sps {
sps[i] = *sp
}
// Not in parallel because we don't want to hold this large allocation live.
runSubTestUserArenaSlice(t, sps, false)
// Test zero-sized types.
t.Run("struct{}", func(t *testing.T) {
arena := NewUserArena()
var x any
x = (*struct{})(nil)
arena.New(&x)
if v := unsafe.Pointer(x.(*struct{})); v != ZeroBase {
t.Errorf("expected zero-sized type to be allocated as zerobase: got %x, want %x", v, ZeroBase)
}
arena.Free()
})
t.Run("[]struct{}", func(t *testing.T) {
arena := NewUserArena()
var sl []struct{}
arena.Slice(&sl, 10)
if v := unsafe.Pointer(&sl[0]); v != ZeroBase {
t.Errorf("expected zero-sized type to be allocated as zerobase: got %x, want %x", v, ZeroBase)
}
arena.Free()
})
t.Run("[]int (cap 0)", func(t *testing.T) {
arena := NewUserArena()
var sl []int
arena.Slice(&sl, 0)
if len(sl) != 0 {
t.Errorf("expected requested zero-sized slice to still have zero length: got %x, want 0", len(sl))
}
arena.Free()
})
})
// Run a GC cycle to get any arenas off the quarantine list.
GC()
if n := GlobalWaitingArenaChunks(); n != 0 {
t.Errorf("expected zero waiting arena chunks, found %d", n)
}
}
func runSubTestUserArenaNew[S comparable](t *testing.T, value *S, parallel bool) {
t.Run(reflect.TypeOf(value).Elem().Name(), func(t *testing.T) {
if parallel {
t.Parallel()
}
// Allocate and write data, enough to exhaust the arena.
//
// This is an underestimate, likely leaving some space in the arena. That's a good thing,
// because it gives us coverage of boundary cases.
n := int(UserArenaChunkBytes / unsafe.Sizeof(*value))
if n == 0 {
n = 1
}
// Create a new arena and do a bunch of operations on it.
arena := NewUserArena()
arenaValues := make([]*S, 0, n)
for j := 0; j < n; j++ {
var x any
x = (*S)(nil)
arena.New(&x)
s := x.(*S)
*s = *value
arenaValues = append(arenaValues, s)
}
// Check integrity of allocated data.
for _, s := range arenaValues {
if *s != *value {
t.Errorf("failed integrity check: got %#v, want %#v", *s, *value)
}
}
// Release the arena.
arena.Free()
})
}
func runSubTestUserArenaSlice[S comparable](t *testing.T, value []S, parallel bool) {
t.Run("[]"+reflect.TypeOf(value).Elem().Name(), func(t *testing.T) {
if parallel {
t.Parallel()
}
// Allocate and write data, enough to exhaust the arena.
//
// This is an underestimate, likely leaving some space in the arena. That's a good thing,
// because it gives us coverage of boundary cases.
n := int(UserArenaChunkBytes / (unsafe.Sizeof(*new(S)) * uintptr(cap(value))))
if n == 0 {
n = 1
}
// Create a new arena and do a bunch of operations on it.
arena := NewUserArena()
arenaValues := make([][]S, 0, n)
for j := 0; j < n; j++ {
var sl []S
arena.Slice(&sl, cap(value))
copy(sl, value)
arenaValues = append(arenaValues, sl)
}
// Check integrity of allocated data.
for _, sl := range arenaValues {
for i := range sl {
got := sl[i]
want := value[i]
if got != want {
t.Errorf("failed integrity check: got %#v, want %#v at index %d", got, want, i)
}
}
}
// Release the arena.
arena.Free()
})
}
func TestUserArenaLiveness(t *testing.T) {
t.Run("Free", func(t *testing.T) {
testUserArenaLiveness(t, false)
})
t.Run("Finalizer", func(t *testing.T) {
testUserArenaLiveness(t, true)
})
}
func testUserArenaLiveness(t *testing.T, useArenaFinalizer bool) {
// Disable the GC so that there's zero chance we try doing anything arena related *during*
// a mark phase, since otherwise a bunch of arenas could end up on the fault list.
defer debug.SetGCPercent(debug.SetGCPercent(-1))
// Defensively ensure that any full arena chunks leftover from previous tests have been cleared.
GC()
GC()
arena := NewUserArena()
// Allocate a few pointer-ful but un-initialized objects so that later we can
// place a reference to heap object at a more interesting location.
for i := 0; i < 3; i++ {
var x any
x = (*mediumPointerOdd)(nil)
arena.New(&x)
}
var x any
x = (*smallPointerMix)(nil)
arena.New(&x)
v := x.(*smallPointerMix)
var safeToFinalize atomic.Bool
var finalized atomic.Bool
v.C = new(smallPointer)
SetFinalizer(v.C, func(_ *smallPointer) {
if !safeToFinalize.Load() {
t.Error("finalized arena-referenced object unexpectedly")
}
finalized.Store(true)
})
// Make sure it stays alive.
GC()
GC()
// In order to ensure the object can be freed, we now need to make sure to use
// the entire arena. Exhaust the rest of the arena.
for i := 0; i < int(UserArenaChunkBytes/unsafe.Sizeof(mediumScalarEven{})); i++ {
var x any
x = (*mediumScalarEven)(nil)
arena.New(&x)
}
// Make sure it stays alive again.
GC()
GC()
v = nil
safeToFinalize.Store(true)
if useArenaFinalizer {
arena = nil
// Try to queue the arena finalizer.
GC()
GC()
// In order for the finalizer we actually want to run to execute,
// we need to make sure this one runs first.
if !BlockUntilEmptyFinalizerQueue(int64(2 * time.Second)) {
t.Fatal("finalizer queue was never emptied")
}
} else {
// Free the arena explicitly.
arena.Free()
}
// Try to queue the object's finalizer that we set earlier.
GC()
GC()
if !BlockUntilEmptyFinalizerQueue(int64(2 * time.Second)) {
t.Fatal("finalizer queue was never emptied")
}
if !finalized.Load() {
t.Error("expected arena-referenced object to be finalized")
}
}
func TestUserArenaClearsPointerBits(t *testing.T) {
// This is a regression test for a serious issue wherein if pointer bits
// aren't properly cleared, it's possible to allocate scalar data down
// into a previously pointer-ful area, causing misinterpretation by the GC.
// Create a large object, grab a pointer into it, and free it.
x := new([8 << 20]byte)
xp := uintptr(unsafe.Pointer(&x[124]))
var finalized atomic.Bool
SetFinalizer(x, func(_ *[8 << 20]byte) {
finalized.Store(true)
})
// Write three chunks worth of pointer data. Three gives us a
// high likelihood that when we write 2 later, we'll get the behavior
// we want.
a := NewUserArena()
for i := 0; i < int(UserArenaChunkBytes/goarch.PtrSize*3); i++ {
var x any
x = (*smallPointer)(nil)
a.New(&x)
}
a.Free()
// Recycle the arena chunks.
GC()
GC()
a = NewUserArena()
for i := 0; i < int(UserArenaChunkBytes/goarch.PtrSize*2); i++ {
var x any
x = (*smallScalar)(nil)
a.New(&x)
v := x.(*smallScalar)
// Write a pointer that should not keep x alive.
*v = smallScalar{xp}
}
KeepAlive(x)
x = nil
// Try to free x.
GC()
GC()
if !BlockUntilEmptyFinalizerQueue(int64(2 * time.Second)) {
t.Fatal("finalizer queue was never emptied")
}
if !finalized.Load() {
t.Fatal("heap allocation kept alive through non-pointer reference")
}
// Clean up the arena.
a.Free()
GC()
GC()
}
func TestUserArenaCloneString(t *testing.T) {
a := NewUserArena()
// A static string (not on heap or arena)
var s = "abcdefghij"
// Create a byte slice in the arena, initialize it with s
var b []byte
a.Slice(&b, len(s))
copy(b, s)
// Create a string as using the same memory as the byte slice, hence in
// the arena. This could be an arena API, but hasn't really been needed
// yet.
as := unsafe.String(&b[0], len(b))
// Clone should make a copy of as, since it is in the arena.
asCopy := UserArenaClone(as)
if unsafe.StringData(as) == unsafe.StringData(asCopy) {
t.Error("Clone did not make a copy")
}
// Clone should make a copy of subAs, since subAs is just part of as and so is in the arena.
subAs := as[1:3]
subAsCopy := UserArenaClone(subAs)
if unsafe.StringData(subAs) == unsafe.StringData(subAsCopy) {
t.Error("Clone did not make a copy")
}
if len(subAs) != len(subAsCopy) {
t.Errorf("Clone made an incorrect copy (bad length): %d -> %d", len(subAs), len(subAsCopy))
} else {
for i := range subAs {
if subAs[i] != subAsCopy[i] {
t.Errorf("Clone made an incorrect copy (data at index %d): %d -> %d", i, subAs[i], subAs[i])
}
}
}
// Clone should not make a copy of doubleAs, since doubleAs will be on the heap.
doubleAs := as + as
doubleAsCopy := UserArenaClone(doubleAs)
if unsafe.StringData(doubleAs) != unsafe.StringData(doubleAsCopy) {
t.Error("Clone should not have made a copy")
}
// Clone should not make a copy of s, since s is a static string.
sCopy := UserArenaClone(s)
if unsafe.StringData(s) != unsafe.StringData(sCopy) {
t.Error("Clone should not have made a copy")
}
a.Free()
}
func TestUserArenaClonePointer(t *testing.T) {
a := NewUserArena()
// Clone should not make a copy of a heap-allocated smallScalar.
x := Escape(new(smallScalar))
xCopy := UserArenaClone(x)
if unsafe.Pointer(x) != unsafe.Pointer(xCopy) {
t.Errorf("Clone should not have made a copy: %#v -> %#v", x, xCopy)
}
// Clone should make a copy of an arena-allocated smallScalar.
var i any
i = (*smallScalar)(nil)
a.New(&i)
xArena := i.(*smallScalar)
xArenaCopy := UserArenaClone(xArena)
if unsafe.Pointer(xArena) == unsafe.Pointer(xArenaCopy) {
t.Errorf("Clone should have made a copy: %#v -> %#v", xArena, xArenaCopy)
}
if *xArena != *xArenaCopy {
t.Errorf("Clone made an incorrect copy copy: %#v -> %#v", *xArena, *xArenaCopy)
}
a.Free()
}
func TestUserArenaCloneSlice(t *testing.T) {
a := NewUserArena()
// A static string (not on heap or arena)
var s = "klmnopqrstuv"
// Create a byte slice in the arena, initialize it with s
var b []byte
a.Slice(&b, len(s))
copy(b, s)
// Clone should make a copy of b, since it is in the arena.
bCopy := UserArenaClone(b)
if unsafe.Pointer(&b[0]) == unsafe.Pointer(&bCopy[0]) {
t.Errorf("Clone did not make a copy: %#v -> %#v", b, bCopy)
}
if len(b) != len(bCopy) {
t.Errorf("Clone made an incorrect copy (bad length): %d -> %d", len(b), len(bCopy))
} else {
for i := range b {
if b[i] != bCopy[i] {
t.Errorf("Clone made an incorrect copy (data at index %d): %d -> %d", i, b[i], bCopy[i])
}
}
}
// Clone should make a copy of bSub, since bSub is just part of b and so is in the arena.
bSub := b[1:3]
bSubCopy := UserArenaClone(bSub)
if unsafe.Pointer(&bSub[0]) == unsafe.Pointer(&bSubCopy[0]) {
t.Errorf("Clone did not make a copy: %#v -> %#v", bSub, bSubCopy)
}
if len(bSub) != len(bSubCopy) {
t.Errorf("Clone made an incorrect copy (bad length): %d -> %d", len(bSub), len(bSubCopy))
} else {
for i := range bSub {
if bSub[i] != bSubCopy[i] {
t.Errorf("Clone made an incorrect copy (data at index %d): %d -> %d", i, bSub[i], bSubCopy[i])
}
}
}
// Clone should not make a copy of bNotArena, since it will not be in an arena.
bNotArena := make([]byte, len(s))
copy(bNotArena, s)
bNotArenaCopy := UserArenaClone(bNotArena)
if unsafe.Pointer(&bNotArena[0]) != unsafe.Pointer(&bNotArenaCopy[0]) {
t.Error("Clone should not have made a copy")
}
a.Free()
}
func TestUserArenaClonePanic(t *testing.T) {
var s string
func() {
x := smallScalar{2}
defer func() {
if v := recover(); v != nil {
s = v.(string)
}
}()
UserArenaClone(x)
}()
if s == "" {
t.Errorf("expected panic from Clone")
}
}