1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/microtask-queue.h"
#include <stddef.h>
#include <algorithm>
#include "src/api.h"
#include "src/base/logging.h"
#include "src/handles-inl.h"
#include "src/isolate.h"
#include "src/objects/microtask-inl.h"
#include "src/roots-inl.h"
#include "src/tracing/trace-event.h"
#include "src/visitors.h"
namespace v8 {
namespace internal {
const size_t MicrotaskQueue::kRingBufferOffset =
OFFSET_OF(MicrotaskQueue, ring_buffer_);
const size_t MicrotaskQueue::kCapacityOffset =
OFFSET_OF(MicrotaskQueue, capacity_);
const size_t MicrotaskQueue::kSizeOffset = OFFSET_OF(MicrotaskQueue, size_);
const size_t MicrotaskQueue::kStartOffset = OFFSET_OF(MicrotaskQueue, start_);
const intptr_t MicrotaskQueue::kMinimumCapacity = 8;
// static
void MicrotaskQueue::SetUpDefaultMicrotaskQueue(Isolate* isolate) {
DCHECK_NULL(isolate->default_microtask_queue());
MicrotaskQueue* microtask_queue = new MicrotaskQueue;
microtask_queue->next_ = microtask_queue;
microtask_queue->prev_ = microtask_queue;
isolate->set_default_microtask_queue(microtask_queue);
}
// static
std::unique_ptr<MicrotaskQueue> MicrotaskQueue::New(Isolate* isolate) {
DCHECK_NOT_NULL(isolate->default_microtask_queue());
std::unique_ptr<MicrotaskQueue> microtask_queue(new MicrotaskQueue);
// Insert the new instance to the next of last MicrotaskQueue instance.
MicrotaskQueue* last = isolate->default_microtask_queue()->prev_;
microtask_queue->next_ = last->next_;
microtask_queue->prev_ = last;
last->next_->prev_ = microtask_queue.get();
last->next_ = microtask_queue.get();
return microtask_queue;
}
MicrotaskQueue::MicrotaskQueue() = default;
MicrotaskQueue::~MicrotaskQueue() {
if (next_ != this) {
DCHECK_NE(prev_, this);
next_->prev_ = prev_;
prev_->next_ = next_;
}
delete[] ring_buffer_;
}
// static
Address MicrotaskQueue::CallEnqueueMicrotask(Isolate* isolate,
intptr_t microtask_queue_pointer,
Address raw_microtask) {
Microtask microtask = Microtask::cast(Object(raw_microtask));
reinterpret_cast<MicrotaskQueue*>(microtask_queue_pointer)
->EnqueueMicrotask(microtask);
return ReadOnlyRoots(isolate).undefined_value().ptr();
}
void MicrotaskQueue::EnqueueMicrotask(Microtask microtask) {
if (size_ == capacity_) {
// Keep the capacity of |ring_buffer_| power of 2, so that the JIT
// implementation can calculate the modulo easily.
intptr_t new_capacity = std::max(kMinimumCapacity, capacity_ << 1);
ResizeBuffer(new_capacity);
}
DCHECK_LT(size_, capacity_);
ring_buffer_[(start_ + size_) % capacity_] = microtask.ptr();
++size_;
}
namespace {
class SetIsRunningMicrotasks {
public:
explicit SetIsRunningMicrotasks(bool* flag) : flag_(flag) {
DCHECK(!*flag_);
*flag_ = true;
}
~SetIsRunningMicrotasks() {
DCHECK(*flag_);
*flag_ = false;
}
private:
bool* flag_;
};
} // namespace
int MicrotaskQueue::RunMicrotasks(Isolate* isolate) {
if (!size()) {
OnCompleted(isolate);
return 0;
}
HandleScope handle_scope(isolate);
MaybeHandle<Object> maybe_exception;
MaybeHandle<Object> maybe_result;
{
SetIsRunningMicrotasks scope(&is_running_microtasks_);
v8::Isolate::SuppressMicrotaskExecutionScope suppress(
reinterpret_cast<v8::Isolate*>(isolate));
HandleScopeImplementer::EnteredContextRewindScope rewind_scope(
isolate->handle_scope_implementer());
TRACE_EVENT0("v8.execute", "RunMicrotasks");
TRACE_EVENT_CALL_STATS_SCOPED(isolate, "v8", "V8.RunMicrotasks");
maybe_result = Execution::TryRunMicrotasks(isolate, this, &maybe_exception);
}
// If execution is terminating, clean up and propagate that to TryCatch scope.
if (maybe_result.is_null() && maybe_exception.is_null()) {
delete[] ring_buffer_;
ring_buffer_ = nullptr;
capacity_ = 0;
size_ = 0;
start_ = 0;
isolate->SetTerminationOnExternalTryCatch();
OnCompleted(isolate);
return -1;
}
DCHECK_EQ(0, size());
OnCompleted(isolate);
// TODO(tzik): Return the number of microtasks run in this round.
return 0;
}
void MicrotaskQueue::IterateMicrotasks(RootVisitor* visitor) {
if (size_) {
// Iterate pending Microtasks as root objects to avoid the write barrier for
// all single Microtask. If this hurts the GC performance, use a FixedArray.
visitor->VisitRootPointers(
Root::kStrongRoots, nullptr, FullObjectSlot(ring_buffer_ + start_),
FullObjectSlot(ring_buffer_ + std::min(start_ + size_, capacity_)));
visitor->VisitRootPointers(
Root::kStrongRoots, nullptr, FullObjectSlot(ring_buffer_),
FullObjectSlot(ring_buffer_ + std::max(start_ + size_ - capacity_,
static_cast<intptr_t>(0))));
}
if (capacity_ <= kMinimumCapacity) {
return;
}
intptr_t new_capacity = capacity_;
while (new_capacity > 2 * size_) {
new_capacity >>= 1;
}
new_capacity = std::max(new_capacity, kMinimumCapacity);
if (new_capacity < capacity_) {
ResizeBuffer(new_capacity);
}
}
void MicrotaskQueue::AddMicrotasksCompletedCallback(
MicrotasksCompletedCallback callback) {
auto pos = std::find(microtasks_completed_callbacks_.begin(),
microtasks_completed_callbacks_.end(), callback);
if (pos != microtasks_completed_callbacks_.end()) return;
microtasks_completed_callbacks_.push_back(callback);
}
void MicrotaskQueue::RemoveMicrotasksCompletedCallback(
MicrotasksCompletedCallback callback) {
auto pos = std::find(microtasks_completed_callbacks_.begin(),
microtasks_completed_callbacks_.end(), callback);
if (pos == microtasks_completed_callbacks_.end()) return;
microtasks_completed_callbacks_.erase(pos);
}
void MicrotaskQueue::FireMicrotasksCompletedCallback(Isolate* isolate) const {
std::vector<MicrotasksCompletedCallback> callbacks(
microtasks_completed_callbacks_);
for (auto& callback : callbacks) {
callback(reinterpret_cast<v8::Isolate*>(isolate));
}
}
void MicrotaskQueue::OnCompleted(Isolate* isolate) {
// TODO(marja): (spec) The discussion about when to clear the KeepDuringJob
// set is still open (whether to clear it after every microtask or once
// during a microtask checkpoint). See also
// https://github.com/tc39/proposal-weakrefs/issues/39 .
isolate->heap()->ClearKeepDuringJobSet();
FireMicrotasksCompletedCallback(isolate);
}
void MicrotaskQueue::ResizeBuffer(intptr_t new_capacity) {
DCHECK_LE(size_, new_capacity);
Address* new_ring_buffer = new Address[new_capacity];
for (intptr_t i = 0; i < size_; ++i) {
new_ring_buffer[i] = ring_buffer_[(start_ + i) % capacity_];
}
delete[] ring_buffer_;
ring_buffer_ = new_ring_buffer;
capacity_ = new_capacity;
start_ = 0;
}
} // namespace internal
} // namespace v8
|
