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
227
228
229
230
231
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "gc/GCParallelTask.h"
#include "mozilla/Maybe.h"
#include "mozilla/TimeStamp.h"
#include "gc/GCContext.h"
#include "gc/GCInternals.h"
#include "gc/ParallelWork.h"
#include "vm/HelperThreadState.h"
#include "vm/Runtime.h"
#include "vm/Time.h"
using namespace js;
using namespace js::gc;
using mozilla::Maybe;
using mozilla::TimeDuration;
using mozilla::TimeStamp;
js::GCParallelTask::~GCParallelTask() {
// The LinkedListElement destructor will remove us from any list we are part
// of without synchronization, so ensure that doesn't happen.
MOZ_DIAGNOSTIC_ASSERT(!isInList());
// Only most-derived classes' destructors may do the join: base class
// destructors run after those for derived classes' members, so a join in a
// base class can't ensure that the task is done using the members. All we
// can do now is check that someone has previously stopped the task.
assertIdle();
}
static bool ShouldMeasureTaskStartDelay() {
// We use many tasks during GC so randomly sample a small fraction for the
// purposes of recording telemetry.
return (rand() % 100) == 0;
}
void js::GCParallelTask::startWithLockHeld(AutoLockHelperThreadState& lock) {
MOZ_ASSERT(CanUseExtraThreads());
MOZ_ASSERT(HelperThreadState().isInitialized(lock));
assertIdle();
maybeQueueTime_ = TimeStamp();
if (ShouldMeasureTaskStartDelay()) {
maybeQueueTime_ = TimeStamp::Now();
}
setDispatched(lock);
HelperThreadState().submitTask(this, lock);
}
void js::GCParallelTask::start() {
if (!CanUseExtraThreads()) {
runFromMainThread();
return;
}
AutoLockHelperThreadState lock;
startWithLockHeld(lock);
}
void js::GCParallelTask::startOrRunIfIdle(AutoLockHelperThreadState& lock) {
if (wasStarted(lock)) {
return;
}
// Join the previous invocation of the task. This will return immediately
// if the thread has never been started.
joinWithLockHeld(lock);
if (!CanUseExtraThreads()) {
runFromMainThread(lock);
return;
}
startWithLockHeld(lock);
}
void js::GCParallelTask::cancelAndWait() {
MOZ_ASSERT(!isCancelled());
cancel_ = true;
join();
cancel_ = false;
}
void js::GCParallelTask::join(Maybe<TimeStamp> deadline) {
AutoLockHelperThreadState lock;
joinWithLockHeld(lock, deadline);
}
void js::GCParallelTask::joinWithLockHeld(AutoLockHelperThreadState& lock,
Maybe<TimeStamp> deadline) {
// Task has not been started; there's nothing to do.
if (isIdle(lock)) {
return;
}
if (isDispatched(lock) && deadline.isNothing()) {
// If the task was dispatched but has not yet started then cancel the task
// and run it from the main thread. This stops us from blocking here when
// the helper threads are busy with other tasks.
cancelDispatchedTask(lock);
runFromMainThread(lock);
} else {
// Otherwise wait for the task to complete.
joinNonIdleTask(deadline, lock);
}
if (isIdle(lock)) {
recordDuration();
}
}
void GCParallelTask::recordDuration() {
if (phaseKind != gcstats::PhaseKind::NONE) {
gc->stats().recordParallelPhase(phaseKind, duration_);
}
}
void js::GCParallelTask::joinNonIdleTask(Maybe<TimeStamp> deadline,
AutoLockHelperThreadState& lock) {
MOZ_ASSERT(!isIdle(lock));
while (!isFinished(lock)) {
TimeDuration timeout = TimeDuration::Forever();
if (deadline) {
TimeStamp now = TimeStamp::Now();
if (*deadline <= now) {
break;
}
timeout = *deadline - now;
}
HelperThreadState().wait(lock, timeout);
}
if (isFinished(lock)) {
setIdle(lock);
}
}
void js::GCParallelTask::cancelDispatchedTask(AutoLockHelperThreadState& lock) {
MOZ_ASSERT(isDispatched(lock));
MOZ_ASSERT(isInList());
remove();
setIdle(lock);
}
void js::GCParallelTask::runFromMainThread(AutoLockHelperThreadState& lock) {
assertIdle();
MOZ_ASSERT(js::CurrentThreadCanAccessRuntime(gc->rt));
state_ = State::Running;
runTask(gc->rt->gcContext(), lock);
state_ = State::Idle;
}
void js::GCParallelTask::runFromMainThread() {
AutoLockHelperThreadState lock;
runFromMainThread(lock);
}
class MOZ_RAII AutoGCContext {
JS::GCContext context;
public:
explicit AutoGCContext(JSRuntime* runtime) : context(runtime) {
MOZ_RELEASE_ASSERT(TlsGCContext.init(),
"Failed to initialize TLS for GC context");
MOZ_ASSERT(!TlsGCContext.get());
TlsGCContext.set(&context);
}
~AutoGCContext() {
MOZ_ASSERT(TlsGCContext.get() == &context);
TlsGCContext.set(nullptr);
}
JS::GCContext* get() { return &context; }
};
void js::GCParallelTask::runHelperThreadTask(AutoLockHelperThreadState& lock) {
setRunning(lock);
AutoGCContext gcContext(gc->rt);
runTask(gcContext.get(), lock);
setFinished(lock);
}
void GCParallelTask::runTask(JS::GCContext* gcx,
AutoLockHelperThreadState& lock) {
// Run the task from either the main thread or a helper thread.
AutoSetThreadGCUse setUse(gcx, use);
// The hazard analysis can't tell what the call to func_ will do but it's not
// allowed to GC.
JS::AutoSuppressGCAnalysis nogc;
TimeStamp timeStart = TimeStamp::Now();
run(lock);
duration_ = TimeSince(timeStart);
if (maybeQueueTime_) {
TimeDuration delay = timeStart - maybeQueueTime_;
gc->rt->metrics().GC_TASK_START_DELAY_US(delay);
}
}
bool js::GCParallelTask::isIdle() const {
AutoLockHelperThreadState lock;
return isIdle(lock);
}
bool js::GCParallelTask::wasStarted() const {
AutoLockHelperThreadState lock;
return wasStarted(lock);
}
/* static */
size_t js::gc::GCRuntime::parallelWorkerCount() const {
return std::min(helperThreadCount.ref(), MaxParallelWorkers);
}
|
