1 // Copyright 2014 The Chromium 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.
5 #include "cc/resources/task_graph_runner.h"
9 #include "base/debug/trace_event.h"
10 #include "base/strings/stringprintf.h"
11 #include "base/threading/thread_restrictions.h"
17 // Helper class for iterating over all dependents of a task.
18 class DependentIterator
{
20 DependentIterator(TaskGraph
* graph
, const Task
* task
)
21 : graph_(graph
), task_(task
), current_index_(-1), current_node_(NULL
) {
25 TaskGraph::Node
& operator->() const {
26 DCHECK_LT(current_index_
, graph_
->edges
.size());
27 DCHECK_EQ(graph_
->edges
[current_index_
].task
, task_
);
28 DCHECK(current_node_
);
29 return *current_node_
;
32 TaskGraph::Node
& operator*() const {
33 DCHECK_LT(current_index_
, graph_
->edges
.size());
34 DCHECK_EQ(graph_
->edges
[current_index_
].task
, task_
);
35 DCHECK(current_node_
);
36 return *current_node_
;
39 // Note: Performance can be improved by keeping edges sorted.
40 DependentIterator
& operator++() {
41 // Find next dependency edge for |task_|.
44 if (current_index_
== graph_
->edges
.size())
46 } while (graph_
->edges
[current_index_
].task
!= task_
);
48 // Now find the node for the dependent of this edge.
49 TaskGraph::Node::Vector::iterator it
=
50 std::find_if(graph_
->nodes
.begin(),
52 TaskGraph::Node::TaskComparator(
53 graph_
->edges
[current_index_
].dependent
));
54 DCHECK(it
!= graph_
->nodes
.end());
55 current_node_
= &(*it
);
60 operator bool() const { return current_index_
< graph_
->edges
.size(); }
65 size_t current_index_
;
66 TaskGraph::Node
* current_node_
;
69 class DependencyMismatchComparator
{
71 explicit DependencyMismatchComparator(const TaskGraph
* graph
)
74 bool operator()(const TaskGraph::Node
& node
) const {
75 return static_cast<size_t>(std::count_if(graph_
->edges
.begin(),
77 DependentComparator(node
.task
))) !=
82 class DependentComparator
{
84 explicit DependentComparator(const Task
* dependent
)
85 : dependent_(dependent
) {}
87 bool operator()(const TaskGraph::Edge
& edge
) const {
88 return edge
.dependent
== dependent_
;
92 const Task
* dependent_
;
95 const TaskGraph
* graph_
;
100 Task::Task() : did_run_(false) {}
104 void Task::WillRun() {
108 void Task::DidRun() { did_run_
= true; }
110 bool Task::HasFinishedRunning() const { return did_run_
; }
112 TaskGraph::TaskGraph() {}
114 TaskGraph::~TaskGraph() {}
116 void TaskGraph::Swap(TaskGraph
* other
) {
117 nodes
.swap(other
->nodes
);
118 edges
.swap(other
->edges
);
121 void TaskGraph::Reset() {
126 TaskGraphRunner::TaskNamespace::TaskNamespace() {}
128 TaskGraphRunner::TaskNamespace::~TaskNamespace() {}
130 TaskGraphRunner::TaskGraphRunner()
132 has_ready_to_run_tasks_cv_(&lock_
),
133 has_namespaces_with_finished_running_tasks_cv_(&lock_
),
134 next_namespace_id_(1),
137 TaskGraphRunner::~TaskGraphRunner() {
139 base::AutoLock
lock(lock_
);
141 DCHECK_EQ(0u, ready_to_run_namespaces_
.size());
142 DCHECK_EQ(0u, namespaces_
.size());
146 NamespaceToken
TaskGraphRunner::GetNamespaceToken() {
147 base::AutoLock
lock(lock_
);
149 NamespaceToken
token(next_namespace_id_
++);
150 DCHECK(namespaces_
.find(token
.id_
) == namespaces_
.end());
154 void TaskGraphRunner::ScheduleTasks(NamespaceToken token
, TaskGraph
* graph
) {
156 "TaskGraphRunner::ScheduleTasks",
160 graph
->edges
.size());
162 DCHECK(token
.IsValid());
163 DCHECK(std::find_if(graph
->nodes
.begin(),
165 DependencyMismatchComparator(graph
)) ==
169 base::AutoLock
lock(lock_
);
173 TaskNamespace
& task_namespace
= namespaces_
[token
.id_
];
175 // First adjust number of dependencies to reflect completed tasks.
176 for (Task::Vector::iterator it
= task_namespace
.completed_tasks
.begin();
177 it
!= task_namespace
.completed_tasks
.end();
179 for (DependentIterator
node_it(graph
, it
->get()); node_it
; ++node_it
) {
180 TaskGraph::Node
& node
= *node_it
;
181 DCHECK_LT(0u, node
.dependencies
);
186 // Build new "ready to run" queue and remove nodes from old graph.
187 task_namespace
.ready_to_run_tasks
.clear();
188 for (TaskGraph::Node::Vector::iterator it
= graph
->nodes
.begin();
189 it
!= graph
->nodes
.end();
191 TaskGraph::Node
& node
= *it
;
193 // Remove any old nodes that are associated with this task. The result is
194 // that the old graph is left with all nodes not present in this graph,
195 // which we use below to determine what tasks need to be canceled.
196 TaskGraph::Node::Vector::iterator old_it
=
197 std::find_if(task_namespace
.graph
.nodes
.begin(),
198 task_namespace
.graph
.nodes
.end(),
199 TaskGraph::Node::TaskComparator(node
.task
));
200 if (old_it
!= task_namespace
.graph
.nodes
.end()) {
201 std::swap(*old_it
, task_namespace
.graph
.nodes
.back());
202 task_namespace
.graph
.nodes
.pop_back();
205 // Task is not ready to run if dependencies are not yet satisfied.
206 if (node
.dependencies
)
209 // Skip if already finished running task.
210 if (node
.task
->HasFinishedRunning())
213 // Skip if already running.
214 if (std::find(task_namespace
.running_tasks
.begin(),
215 task_namespace
.running_tasks
.end(),
216 node
.task
) != task_namespace
.running_tasks
.end())
219 task_namespace
.ready_to_run_tasks
.push_back(
220 PrioritizedTask(node
.task
, node
.priority
));
223 // Rearrange the elements in |ready_to_run_tasks| in such a way that they
225 std::make_heap(task_namespace
.ready_to_run_tasks
.begin(),
226 task_namespace
.ready_to_run_tasks
.end(),
227 CompareTaskPriority
);
230 task_namespace
.graph
.Swap(graph
);
232 // Determine what tasks in old graph need to be canceled.
233 for (TaskGraph::Node::Vector::iterator it
= graph
->nodes
.begin();
234 it
!= graph
->nodes
.end();
236 TaskGraph::Node
& node
= *it
;
238 // Skip if already finished running task.
239 if (node
.task
->HasFinishedRunning())
242 // Skip if already running.
243 if (std::find(task_namespace
.running_tasks
.begin(),
244 task_namespace
.running_tasks
.end(),
245 node
.task
) != task_namespace
.running_tasks
.end())
248 DCHECK(std::find(task_namespace
.completed_tasks
.begin(),
249 task_namespace
.completed_tasks
.end(),
250 node
.task
) == task_namespace
.completed_tasks
.end());
251 task_namespace
.completed_tasks
.push_back(node
.task
);
254 // Build new "ready to run" task namespaces queue.
255 ready_to_run_namespaces_
.clear();
256 for (TaskNamespaceMap::iterator it
= namespaces_
.begin();
257 it
!= namespaces_
.end();
259 if (!it
->second
.ready_to_run_tasks
.empty())
260 ready_to_run_namespaces_
.push_back(&it
->second
);
263 // Rearrange the task namespaces in |ready_to_run_namespaces_| in such a way
264 // that they form a heap.
265 std::make_heap(ready_to_run_namespaces_
.begin(),
266 ready_to_run_namespaces_
.end(),
267 CompareTaskNamespacePriority
);
269 // If there is more work available, wake up worker thread.
270 if (!ready_to_run_namespaces_
.empty())
271 has_ready_to_run_tasks_cv_
.Signal();
275 void TaskGraphRunner::WaitForTasksToFinishRunning(NamespaceToken token
) {
276 TRACE_EVENT0("cc", "TaskGraphRunner::WaitForTasksToFinishRunning");
278 DCHECK(token
.IsValid());
281 base::AutoLock
lock(lock_
);
283 TaskNamespaceMap::const_iterator it
= namespaces_
.find(token
.id_
);
284 if (it
== namespaces_
.end())
287 const TaskNamespace
& task_namespace
= it
->second
;
289 while (!HasFinishedRunningTasksInNamespace(&task_namespace
))
290 has_namespaces_with_finished_running_tasks_cv_
.Wait();
292 // There may be other namespaces that have finished running tasks, so wake
293 // up another origin thread.
294 has_namespaces_with_finished_running_tasks_cv_
.Signal();
298 void TaskGraphRunner::CollectCompletedTasks(NamespaceToken token
,
299 Task::Vector
* completed_tasks
) {
300 TRACE_EVENT0("cc", "TaskGraphRunner::CollectCompletedTasks");
302 DCHECK(token
.IsValid());
305 base::AutoLock
lock(lock_
);
307 TaskNamespaceMap::iterator it
= namespaces_
.find(token
.id_
);
308 if (it
== namespaces_
.end())
311 TaskNamespace
& task_namespace
= it
->second
;
313 DCHECK_EQ(0u, completed_tasks
->size());
314 completed_tasks
->swap(task_namespace
.completed_tasks
);
315 if (!HasFinishedRunningTasksInNamespace(&task_namespace
))
318 // Remove namespace if finished running tasks.
319 DCHECK_EQ(0u, task_namespace
.completed_tasks
.size());
320 DCHECK_EQ(0u, task_namespace
.ready_to_run_tasks
.size());
321 DCHECK_EQ(0u, task_namespace
.running_tasks
.size());
322 namespaces_
.erase(it
);
326 void TaskGraphRunner::Shutdown() {
327 base::AutoLock
lock(lock_
);
329 DCHECK_EQ(0u, ready_to_run_namespaces_
.size());
330 DCHECK_EQ(0u, namespaces_
.size());
335 // Wake up a worker so it knows it should exit. This will cause all workers
336 // to exit as each will wake up another worker before exiting.
337 has_ready_to_run_tasks_cv_
.Signal();
340 void TaskGraphRunner::Run() {
341 base::AutoLock
lock(lock_
);
344 if (ready_to_run_namespaces_
.empty()) {
345 // Exit when shutdown is set and no more tasks are pending.
349 // Wait for more tasks.
350 has_ready_to_run_tasks_cv_
.Wait();
354 RunTaskWithLockAcquired();
357 // We noticed we should exit. Wake up the next worker so it knows it should
358 // exit as well (because the Shutdown() code only signals once).
359 has_ready_to_run_tasks_cv_
.Signal();
362 void TaskGraphRunner::RunUntilIdle() {
363 base::AutoLock
lock(lock_
);
365 while (!ready_to_run_namespaces_
.empty())
366 RunTaskWithLockAcquired();
369 void TaskGraphRunner::RunTaskWithLockAcquired() {
370 TRACE_EVENT0("toplevel", "TaskGraphRunner::RunTask");
372 lock_
.AssertAcquired();
373 DCHECK(!ready_to_run_namespaces_
.empty());
375 // Take top priority TaskNamespace from |ready_to_run_namespaces_|.
376 std::pop_heap(ready_to_run_namespaces_
.begin(),
377 ready_to_run_namespaces_
.end(),
378 CompareTaskNamespacePriority
);
379 TaskNamespace
* task_namespace
= ready_to_run_namespaces_
.back();
380 ready_to_run_namespaces_
.pop_back();
381 DCHECK(!task_namespace
->ready_to_run_tasks
.empty());
383 // Take top priority task from |ready_to_run_tasks|.
384 std::pop_heap(task_namespace
->ready_to_run_tasks
.begin(),
385 task_namespace
->ready_to_run_tasks
.end(),
386 CompareTaskPriority
);
387 scoped_refptr
<Task
> task(task_namespace
->ready_to_run_tasks
.back().task
);
388 task_namespace
->ready_to_run_tasks
.pop_back();
390 // Add task namespace back to |ready_to_run_namespaces_| if not empty after
391 // taking top priority task.
392 if (!task_namespace
->ready_to_run_tasks
.empty()) {
393 ready_to_run_namespaces_
.push_back(task_namespace
);
394 std::push_heap(ready_to_run_namespaces_
.begin(),
395 ready_to_run_namespaces_
.end(),
396 CompareTaskNamespacePriority
);
399 // Add task to |running_tasks|.
400 task_namespace
->running_tasks
.push_back(task
.get());
402 // There may be more work available, so wake up another worker thread.
403 has_ready_to_run_tasks_cv_
.Signal();
405 // Call WillRun() before releasing |lock_| and running task.
409 base::AutoUnlock
unlock(lock_
);
411 task
->RunOnWorkerThread();
414 // This will mark task as finished running.
417 // Remove task from |running_tasks|.
418 TaskVector::iterator it
= std::find(task_namespace
->running_tasks
.begin(),
419 task_namespace
->running_tasks
.end(),
421 DCHECK(it
!= task_namespace
->running_tasks
.end());
422 std::swap(*it
, task_namespace
->running_tasks
.back());
423 task_namespace
->running_tasks
.pop_back();
425 // Now iterate over all dependents to decrement dependencies and check if they
427 bool ready_to_run_namespaces_has_heap_properties
= true;
428 for (DependentIterator
it(&task_namespace
->graph
, task
.get()); it
; ++it
) {
429 TaskGraph::Node
& dependent_node
= *it
;
431 DCHECK_LT(0u, dependent_node
.dependencies
);
432 dependent_node
.dependencies
--;
433 // Task is ready if it has no dependencies. Add it to |ready_to_run_tasks_|.
434 if (!dependent_node
.dependencies
) {
435 bool was_empty
= task_namespace
->ready_to_run_tasks
.empty();
436 task_namespace
->ready_to_run_tasks
.push_back(
437 PrioritizedTask(dependent_node
.task
, dependent_node
.priority
));
438 std::push_heap(task_namespace
->ready_to_run_tasks
.begin(),
439 task_namespace
->ready_to_run_tasks
.end(),
440 CompareTaskPriority
);
441 // Task namespace is ready if it has at least one ready to run task. Add
442 // it to |ready_to_run_namespaces_| if it just become ready.
444 DCHECK(std::find(ready_to_run_namespaces_
.begin(),
445 ready_to_run_namespaces_
.end(),
446 task_namespace
) == ready_to_run_namespaces_
.end());
447 ready_to_run_namespaces_
.push_back(task_namespace
);
449 ready_to_run_namespaces_has_heap_properties
= false;
453 // Rearrange the task namespaces in |ready_to_run_namespaces_| in such a way
454 // that they yet again form a heap.
455 if (!ready_to_run_namespaces_has_heap_properties
) {
456 std::make_heap(ready_to_run_namespaces_
.begin(),
457 ready_to_run_namespaces_
.end(),
458 CompareTaskNamespacePriority
);
461 // Finally add task to |completed_tasks_|.
462 task_namespace
->completed_tasks
.push_back(task
);
464 // If namespace has finished running all tasks, wake up origin thread.
465 if (HasFinishedRunningTasksInNamespace(task_namespace
))
466 has_namespaces_with_finished_running_tasks_cv_
.Signal();
469 } // namespace internal