| Flutter Impeller |

fence_waiter_vk.cc
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "impeller/renderer/backend/vulkan/fence_waiter_vk.h"
6
7 #include <algorithm>
8 #include <chrono>
9 #include <utility>
10
11 #include "flutter/fml/cpu_affinity.h"
12 #include "flutter/fml/thread.h"
13 #include "flutter/fml/trace_event.h"
14 #include "impeller/base/validation.h"
15
16 namespace impeller {
17
18 class WaitSetEntry {
19 public:
20 static std::shared_ptr<WaitSetEntry> Create(vk::UniqueFence p_fence,
21 const fml::closure& p_callback) {
22 return std::shared_ptr<WaitSetEntry>(
23 new WaitSetEntry(std::move(p_fence), p_callback));
24 }
25
26 void UpdateSignalledStatus(const vk::Device& device) {
27 if (is_signalled_) {
28 return;
29 }
30 is_signalled_ = device.getFenceStatus(fence_.get()) == vk::Result::eSuccess;
31 }
32
33 const vk::Fence& GetFence() const { return fence_.get(); }
34
35 bool IsSignalled() const { return is_signalled_; }
36
37 private:
38 vk::UniqueFence fence_;
39 fml::ScopedCleanupClosure callback_;
40 bool is_signalled_ = false;
41
42 WaitSetEntry(vk::UniqueFence p_fence, const fml::closure& p_callback)
43 : fence_(std::move(p_fence)),
44 callback_(fml::ScopedCleanupClosure{p_callback}) {}
45
46 WaitSetEntry(const WaitSetEntry&) = delete;
47
48 WaitSetEntry(WaitSetEntry&&) = delete;
49
50 WaitSetEntry& operator=(const WaitSetEntry&) = delete;
51
52 WaitSetEntry& operator=(WaitSetEntry&&) = delete;
53 };
54
55 FenceWaiterVK::FenceWaiterVK(std::weak_ptr<DeviceHolder> device_holder)
56 : device_holder_(std::move(device_holder)) {
57 waiter_thread_ = std::make_unique<std::thread>([&]() { Main(); });
58 }
59
60 FenceWaiterVK::~FenceWaiterVK() {
61 Terminate();
62 waiter_thread_->join();
63 }
64
65 bool FenceWaiterVK::AddFence(vk::UniqueFence fence,
66 const fml::closure& callback) {
67 if (!fence || !callback) {
68 return false;
69 }
70 {
71 // Maintain the invariant that terminate_ is accessed only under the lock.
72 std::scoped_lock lock(wait_set_mutex_);
73 if (terminate_) {
74 return false;
75 }
76 wait_set_.emplace_back(WaitSetEntry::Create(std::move(fence), callback));
77 }
78 wait_set_cv_.notify_one();
79 return true;
80 }
81
82 static std::vector<vk::Fence> GetFencesForWaitSet(const WaitSet& set) {
83 std::vector<vk::Fence> fences;
84 for (const auto& entry : set) {
85 if (!entry->IsSignalled()) {
86 fences.emplace_back(entry->GetFence());
87 }
88 }
89 return fences;
90 }
91
92 void FenceWaiterVK::Main() {
93 fml::Thread::SetCurrentThreadName(
94 fml::Thread::ThreadConfig{"io.flutter.impeller.fence_waiter"});
95 // Since this thread mostly waits on fences, it doesn't need to be fast.
96 fml::RequestAffinity(fml::CpuAffinity::kEfficiency);
97
98 while (true) {
99 // We'll read the terminate_ flag within the lock below.
100 bool terminate = false;
101
102 {
103 std::unique_lock lock(wait_set_mutex_);
104
105 // If there are no fences to wait on, wait on the condition variable.
106 wait_set_cv_.wait(lock,
107 [&]() { return !wait_set_.empty() || terminate_; });
108
109 // Still under the lock, check if the waiter has been terminated.
110 terminate = terminate_;
111 }
112
113 if (terminate) {
114 WaitUntilEmpty();
115 break;
116 }
117
118 if (!Wait()) {
119 break;
120 }
121 }
122 }
123
124 void FenceWaiterVK::WaitUntilEmpty() {
125 // Note, there is no lock because once terminate_ is set to true, no other
126 // fence can be added to the wait set. Just in case, here's a FML_DCHECK:
127 FML_DCHECK(terminate_) << "Fence waiter must be terminated.";
128 while (!wait_set_.empty() && Wait()) {
129 // Intentionally empty.
130 }
131 }
132
133 bool FenceWaiterVK::Wait() {
134 // Snapshot the wait set and wait on the fences.
135 WaitSet wait_set;
136 {
137 std::scoped_lock lock(wait_set_mutex_);
138 wait_set = wait_set_;
139 }
140
141 using namespace std::literals::chrono_literals;
142
143 // Check if the context had died in the meantime.
144 auto device_holder = device_holder_.lock();
145 if (!device_holder) {
146 return false;
147 }
148
149 const auto& device = device_holder->GetDevice();
150 // Wait for one or more fences to be signaled. Any additional fences added
151 // to the waiter will be serviced in the next pass. If a fence that is going
152 // to be signaled at an abnormally long deadline is the only one in the set,
153 // a timeout will bail out the wait.
154 auto fences = GetFencesForWaitSet(wait_set);
155 if (fences.empty()) {
156 return true;
157 }
158
159 auto result = device.waitForFences(
160 /*fenceCount=*/fences.size(),
161 /*pFences=*/fences.data(),
162 /*waitAll=*/false,
163 /*timeout=*/std::chrono::nanoseconds{100ms}.count());
164 if (!(result == vk::Result::eSuccess || result == vk::Result::eTimeout)) {
165 VALIDATION_LOG << "Fence waiter encountered an unexpected error. Tearing "
166 "down the waiter thread.";
167 return false;
168 }
169
170 // One or more fences have been signaled. Find out which ones and update
171 // their signaled statuses.
172 {
173 TRACE_EVENT0("impeller", "CheckFenceStatus");
174 for (auto& entry : wait_set) {
175 entry->UpdateSignalledStatus(device);
176 }
177 wait_set.clear();
178 }
179
180 // Quickly acquire the wait set lock and erase signaled entries. Make sure
181 // the mutex is unlocked before calling the destructors of the erased
182 // entries. These might touch allocators.
183 WaitSet erased_entries;
184 {
185 static constexpr auto is_signalled = [](const auto& entry) {
186 return entry->IsSignalled();
187 };
188 std::scoped_lock lock(wait_set_mutex_);
189
190 // TODO(matanlurey): Iterate the list 1x by copying is_signaled into erased.
191 std::copy_if(wait_set_.begin(), wait_set_.end(),
192 std::back_inserter(erased_entries), is_signalled);
193 wait_set_.erase(
194 std::remove_if(wait_set_.begin(), wait_set_.end(), is_signalled),
195 wait_set_.end());
196 }
197
198 {
199 TRACE_EVENT0("impeller", "ClearSignaledFences");
200 // Erase the erased entries which will invoke callbacks.
201 erased_entries.clear(); // Bit redundant because of scope but hey.
202 }
203
204 return true;
205 }
206
207 void FenceWaiterVK::Terminate() {
208 {
209 std::scoped_lock lock(wait_set_mutex_);
210 terminate_ = true;
211 }
212 wait_set_cv_.notify_one();
213 }
214
215 } // namespace impeller
impeller::WaitSetEntry::Create
static std::shared_ptr< WaitSetEntry > Create(vk::UniqueFence p_fence, const fml::closure &p_callback)
Definition: fence_waiter_vk.cc:20
impeller::GetFencesForWaitSet
static std::vector< vk::Fence > GetFencesForWaitSet(const WaitSet &set)
Definition: fence_waiter_vk.cc:82
fence_waiter_vk.h
impeller::WaitSet
std::vector< std::shared_ptr< WaitSetEntry > > WaitSet
Definition: fence_waiter_vk.h:25
impeller::WaitSetEntry::GetFence
const vk::Fence & GetFence() const
Definition: fence_waiter_vk.cc:33
impeller::FenceWaiterVK::AddFence
bool AddFence(vk::UniqueFence fence, const fml::closure &callback)
Definition: fence_waiter_vk.cc:65
impeller::Main
bool Main(const fml::CommandLine &command_line)
Definition: shader_archive_main.cc:13
validation.h
VALIDATION_LOG
#define VALIDATION_LOG
Definition: validation.h:67
impeller::WaitSetEntry
Definition: fence_waiter_vk.cc:18
std
Definition: comparable.h:95
impeller::FenceWaiterVK::Terminate
void Terminate()
Definition: fence_waiter_vk.cc:207
impeller::WaitSetEntry::IsSignalled
bool IsSignalled() const
Definition: fence_waiter_vk.cc:35
impeller::FenceWaiterVK::~FenceWaiterVK
~FenceWaiterVK()
Definition: fence_waiter_vk.cc:60
impeller::WaitSetEntry::UpdateSignalledStatus
void UpdateSignalledStatus(const vk::Device &device)
Definition: fence_waiter_vk.cc:26
impeller
Definition: aiks_context.cc:10