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
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
content / browser / scheduler / browser_ui_thread_scheduler.cc [blame]
// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/scheduler/browser_ui_thread_scheduler.h"
#include <utility>
#include "base/feature_list.h"
#include "base/memory/ptr_util.h"
#include "base/message_loop/message_pump.h"
#include "base/message_loop/message_pump_type.h"
#include "base/notreached.h"
#include "base/process/process.h"
#include "base/run_loop.h"
#include "base/task/sequence_manager/sequence_manager.h"
#include "base/task/sequence_manager/sequence_manager_impl.h"
#include "base/task/sequence_manager/task_queue.h"
#include "base/task/sequence_manager/time_domain.h"
#include "base/threading/platform_thread.h"
#include "base/trace_event/trace_event.h"
#include "build/build_config.h"
#include "content/browser/scheduler/browser_task_priority.h"
#include "content/browser/scheduler/browser_task_queues.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/common/content_features.h"
namespace {
content::BrowserUIThreadScheduler* g_browser_ui_thread_scheduler = nullptr;
bool IsActiveScrollState(
content::BrowserUIThreadScheduler::ScrollState scroll_state) {
return scroll_state ==
content::BrowserUIThreadScheduler::ScrollState::kFlingActive ||
scroll_state == content::BrowserUIThreadScheduler::ScrollState::
kGestureScrollActive;
}
} // namespace
namespace content {
namespace features {
// When the "BrowserPrioritizeNativeWork" feature is enabled, the main thread
// will process native messages between each batch of application tasks for some
// duration after an input event. The duration is controlled by the
// "prioritize_for_next_ms" feature param. Special case: If
// "prioritize_for_next_ms" is TimeDelta::Max(), native messages will be
// processed between each batch of application tasks, independently from input
// events.
//
// The goal is to reduce jank by processing subsequent input events sooner after
// a first input event is received. Checking for native messages more frequently
// incurs some overhead, but allows the browser to handle input more
// consistently.
BASE_FEATURE(kBrowserPrioritizeNativeWork,
"BrowserPrioritizeNativeWork",
base::FEATURE_DISABLED_BY_DEFAULT);
constexpr base::FeatureParam<base::TimeDelta>
kBrowserPrioritizeNativeWorkAfterInputForNMsParam{
&kBrowserPrioritizeNativeWork, "prioritize_for_next_ms",
base::TimeDelta::Max()};
// Feature to defer tasks on the UI thread to prioritise input.
BASE_FEATURE(kBrowserDeferUIThreadTasks,
"BrowserDeferUIThreadTasks",
base::FEATURE_DISABLED_BY_DEFAULT);
constexpr base::FeatureParam<bool> kDeferNormalOrLessPriorityTasks{
&kBrowserDeferUIThreadTasks, "defer_normal_or_less_priority_tasks", false};
constexpr base::FeatureParam<bool> kDeferKnownLongRunningTasks{
&kBrowserDeferUIThreadTasks, "defer_known_long_running_tasks", false};
} // namespace features
BrowserUIThreadScheduler::UserInputActiveHandle::UserInputActiveHandle(
BrowserUIThreadScheduler* scheduler)
: scheduler_(scheduler) {
DCHECK_CURRENTLY_ON(BrowserThread::UI);
DCHECK(scheduler_);
DCHECK_GE(scheduler_->user_input_active_handle_count, 0);
++scheduler_->user_input_active_handle_count;
if (scheduler_->user_input_active_handle_count == 1) {
TRACE_EVENT("input", "RenderWidgetHostImpl::UserInputStarted");
scheduler_->DidStartUserInput();
}
}
BrowserUIThreadScheduler::UserInputActiveHandle::UserInputActiveHandle(
UserInputActiveHandle&& other) {
MoveFrom(&other);
}
BrowserUIThreadScheduler::UserInputActiveHandle&
BrowserUIThreadScheduler::UserInputActiveHandle::operator=(
UserInputActiveHandle&& other) {
MoveFrom(&other);
return *this;
}
void BrowserUIThreadScheduler::UserInputActiveHandle::MoveFrom(
UserInputActiveHandle* other) {
scheduler_ = other->scheduler_;
// Prevent the other's deconstructor from decrementing
// |user_input_active_handle_counter|.
other->scheduler_ = nullptr;
}
BrowserUIThreadScheduler::UserInputActiveHandle::~UserInputActiveHandle() {
DCHECK_CURRENTLY_ON(BrowserThread::UI);
if (!scheduler_) {
return;
}
DCHECK_GE(scheduler_->user_input_active_handle_count, 1);
--scheduler_->user_input_active_handle_count;
if (scheduler_->user_input_active_handle_count == 0) {
scheduler_->DidEndUserInput();
}
}
BrowserUIThreadScheduler::~BrowserUIThreadScheduler() = default;
// static
std::unique_ptr<BrowserUIThreadScheduler>
BrowserUIThreadScheduler::CreateForTesting(
base::sequence_manager::SequenceManager* sequence_manager) {
return base::WrapUnique(new BrowserUIThreadScheduler(sequence_manager));
}
BrowserUIThreadScheduler* BrowserUIThreadScheduler::Get() {
DCHECK(g_browser_ui_thread_scheduler);
return g_browser_ui_thread_scheduler;
}
BrowserUIThreadScheduler::BrowserUIThreadScheduler()
: owned_sequence_manager_(
base::sequence_manager::CreateUnboundSequenceManager(
base::sequence_manager::SequenceManager::Settings::Builder()
.SetMessagePumpType(base::MessagePumpType::UI)
.SetCanRunTasksByBatches(true)
.SetPrioritySettings(
internal::CreateBrowserTaskPrioritySettings())
.Build())),
task_queues_(BrowserThread::UI, owned_sequence_manager_.get()),
queue_enabled_voters_(task_queues_.CreateQueueEnabledVoters()),
handle_(task_queues_.GetHandle()) {
CommonSequenceManagerSetup(owned_sequence_manager_.get());
owned_sequence_manager_->SetDefaultTaskRunner(
handle_->GetDefaultTaskRunner());
owned_sequence_manager_->BindToMessagePump(
base::MessagePump::Create(base::MessagePumpType::UI));
g_browser_ui_thread_scheduler = this;
}
BrowserUIThreadScheduler::BrowserUIThreadScheduler(
base::sequence_manager::SequenceManager* sequence_manager)
: task_queues_(BrowserThread::UI, sequence_manager),
queue_enabled_voters_(task_queues_.CreateQueueEnabledVoters()),
handle_(task_queues_.GetHandle()) {
CommonSequenceManagerSetup(sequence_manager);
g_browser_ui_thread_scheduler = this;
}
void BrowserUIThreadScheduler::CommonSequenceManagerSetup(
base::sequence_manager::SequenceManager* sequence_manager) {
DCHECK_EQ(static_cast<size_t>(sequence_manager->GetPriorityCount()),
static_cast<size_t>(internal::BrowserTaskPriority::kPriorityCount));
sequence_manager->EnableCrashKeys("ui_scheduler_async_stack");
}
BrowserUIThreadScheduler::UserInputActiveHandle
BrowserUIThreadScheduler::OnUserInputStart() {
return BrowserUIThreadScheduler::UserInputActiveHandle(this);
}
void BrowserUIThreadScheduler::DidStartUserInput() {
if (!browser_prioritize_native_work_ ||
browser_prioritize_native_work_after_input_end_ms_.is_inf()) {
return;
}
owned_sequence_manager_->PrioritizeYieldingToNative(base::TimeTicks::Max());
}
void BrowserUIThreadScheduler::OnScrollStateUpdate(ScrollState scroll_state) {
if (browser_enable_deferring_ui_thread_tasks_) {
UpdatePolicyOnScrollStateUpdate(scroll_state_, scroll_state);
}
scroll_state_ = scroll_state;
}
void BrowserUIThreadScheduler::UpdatePolicyOnScrollStateUpdate(
ScrollState old_state,
ScrollState new_state) {
TRACE_EVENT("input",
"BrowserUIThreadScheduler::UpdatePolicyOnScrollStateUpdate",
"enabled", IsActiveScrollState(new_state));
bool state_change =
IsActiveScrollState(old_state) != IsActiveScrollState(new_state);
if (!state_change) {
return;
}
current_policy_.should_defer_task_queues_ = IsActiveScrollState(new_state);
UpdateTaskQueueStates();
}
void BrowserUIThreadScheduler::UpdateTaskQueueStates() {
for (unsigned int i = 0; i < task_queues_.kNumQueueTypes; i++) {
QueueType type = static_cast<QueueType>(i);
GetBrowserTaskRunnerVoter(type).SetVoteToEnable(
current_policy_.IsQueueEnabled(type));
}
}
bool BrowserUIThreadScheduler::Policy::IsQueueEnabled(
BrowserTaskQueues::QueueType task_queue) const {
if (!should_defer_task_queues_) {
return true;
}
switch (task_queue) {
case BrowserTaskQueues::QueueType::kDeferrableUserBlocking:
return !(should_defer_task_queues_ && defer_known_long_running_tasks_);
case BrowserTaskQueues::QueueType::kBestEffort:
case BrowserTaskQueues::QueueType::kUserVisible:
case BrowserTaskQueues::QueueType::kUserBlocking:
return !(should_defer_task_queues_ &&
defer_normal_or_lower_priority_tasks_);
// TODO(b/261554018): defer the default task queue after pumping the
// priority of scoped blocking calls from renderer to UI main to
// avoid deadlocks on deferring default queue.
case BrowserTaskQueues::QueueType::kDefault:
case BrowserTaskQueues::QueueType::kUserInput:
case BrowserTaskQueues::QueueType::kNavigationNetworkResponse:
case BrowserTaskQueues::QueueType::kServiceWorkerStorageControlResponse:
case BrowserTaskQueues::QueueType::kBeforeUnloadBrowserResponse:
return true;
}
NOTREACHED_IN_MIGRATION();
}
void BrowserUIThreadScheduler::DidEndUserInput() {
if (!browser_prioritize_native_work_ ||
browser_prioritize_native_work_after_input_end_ms_.is_inf()) {
return;
}
owned_sequence_manager_->PrioritizeYieldingToNative(
base::TimeTicks::Now() +
browser_prioritize_native_work_after_input_end_ms_);
}
void BrowserUIThreadScheduler::PostFeatureListSetup() {
if (base::FeatureList::IsEnabled(features::kBrowserPrioritizeNativeWork)) {
EnableBrowserPrioritizesNativeWork();
}
if (base::FeatureList::IsEnabled(features::kBrowserDeferUIThreadTasks)) {
EnableDeferringBrowserUIThreadTasks();
}
}
void BrowserUIThreadScheduler::EnableBrowserPrioritizesNativeWork() {
browser_prioritize_native_work_after_input_end_ms_ =
features::kBrowserPrioritizeNativeWorkAfterInputForNMsParam.Get();
// Rather than just enable immediately we post a task at default priority.
// This ensures most start up work should be finished before we start using
// this policy.
//
// TODO(nuskos): Switch this to use ThreadControllerObserver after start up
// notification once available on android.
handle_->GetDefaultTaskRunner()->PostTask(
FROM_HERE,
base::BindOnce(
[](BrowserUIThreadScheduler* scheduler) {
scheduler->browser_prioritize_native_work_ = true;
if (scheduler->browser_prioritize_native_work_after_input_end_ms_
.is_inf()) {
// We will always prioritize yielding to native if the
// experiment is enabled but the delay after input is infinity.
// So enable it now.
scheduler->owned_sequence_manager_->PrioritizeYieldingToNative(
base::TimeTicks::Max());
}
},
base::Unretained(this)));
}
void BrowserUIThreadScheduler::EnableDeferringBrowserUIThreadTasks() {
// Initialize feature parameters. This can't be done in the constructor
// because the FeatureList hasn't been initialized when the
// BrowserUIThreadScheduler is created.
current_policy_.defer_normal_or_lower_priority_tasks_ =
features::kDeferNormalOrLessPriorityTasks.Get();
current_policy_.defer_known_long_running_tasks_ =
features::kDeferKnownLongRunningTasks.Get();
browser_enable_deferring_ui_thread_tasks_ = true;
}
} // namespace content