content/renderer/raster_worker_pool.cc

// Copyright 2015 The Chromium 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 "raster_worker_pool.h"

#include "base/strings/stringprintf.h"

namespace content {

// A sequenced task runner which posts tasks to a RasterWorkerPool.
class RasterWorkerPool::RasterWorkerPoolSequencedTaskRunner
    : public base::SequencedTaskRunner {
 public:
  RasterWorkerPoolSequencedTaskRunner(cc::TaskGraphRunner* task_graph_runner)
      : task_graph_runner_(task_graph_runner),
        namespace_token_(task_graph_runner->GetNamespaceToken()) {}

  // Overridden from base::TaskRunner:
  bool PostDelayedTask(const tracked_objects::Location& from_here,
                       const base::Closure& task,
                       base::TimeDelta delay) override {
    return PostNonNestableDelayedTask(from_here, task, delay);
  }
  bool RunsTasksOnCurrentThread() const override { return true; }

  // Overridden from base::SequencedTaskRunner:
  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
                                  const base::Closure& task,
                                  base::TimeDelta delay) override {
    base::AutoLock lock(lock_);

    // Remove completed tasks.
    DCHECK(completed_tasks_.empty());
    task_graph_runner_->CollectCompletedTasks(namespace_token_,
                                              &completed_tasks_);

    tasks_.erase(tasks_.begin(), tasks_.begin() + completed_tasks_.size());

    tasks_.push_back(make_scoped_refptr(new ClosureTask(task)));
    graph_.Reset();
    for (const auto& graph_task : tasks_) {
      int dependencies = 0;
      if (!graph_.nodes.empty())
        dependencies = 1;

      cc::TaskGraph::Node node(graph_task.get(), 0, dependencies);
      if (dependencies) {
        graph_.edges.push_back(
            cc::TaskGraph::Edge(graph_.nodes.back().task, node.task));
      }
      graph_.nodes.push_back(node);
    }
    task_graph_runner_->ScheduleTasks(namespace_token_, &graph_);
    completed_tasks_.clear();
    return true;
  }

 private:
  ~RasterWorkerPoolSequencedTaskRunner() override {
    task_graph_runner_->WaitForTasksToFinishRunning(namespace_token_);
    task_graph_runner_->CollectCompletedTasks(namespace_token_,
                                              &completed_tasks_);
  };

  cc::TaskGraphRunner* const task_graph_runner_;

  // Lock to exclusively access all the following members that are used to
  // implement the SequencedTaskRunner interfaces.
  base::Lock lock_;
  // Namespace used to schedule tasks in the task graph runner.
  cc::NamespaceToken namespace_token_;
  // List of tasks currently queued up for execution.
  cc::Task::Vector tasks_;
  // Graph object used for scheduling tasks.
  cc::TaskGraph graph_;
  // Cached vector to avoid allocation when getting the list of complete
  // tasks.
  cc::Task::Vector completed_tasks_;
};

RasterWorkerPool::RasterWorkerPool()
    : namespace_token_(task_graph_runner_.GetNamespaceToken()) {}

void RasterWorkerPool::Start(
    int num_threads,
    const base::SimpleThread::Options& thread_options) {
  DCHECK(threads_.empty());
  while (threads_.size() < static_cast<size_t>(num_threads)) {
    scoped_ptr<base::DelegateSimpleThread> thread(
        new base::DelegateSimpleThread(
            this, base::StringPrintf("CompositorTileWorker%u",
                                     static_cast<unsigned>(threads_.size() + 1))
                      .c_str(),
            thread_options));
    thread->Start();
    threads_.push_back(thread.Pass());
  }
}

void RasterWorkerPool::Shutdown() {
  task_graph_runner_.WaitForTasksToFinishRunning(namespace_token_);
  task_graph_runner_.CollectCompletedTasks(namespace_token_, &completed_tasks_);
  // Shutdown raster threads.
  task_graph_runner_.Shutdown();
  while (!threads_.empty()) {
    threads_.back()->Join();
    threads_.pop_back();
  }
}

// Overridden from base::TaskRunner:
bool RasterWorkerPool::PostDelayedTask(
    const tracked_objects::Location& from_here,
    const base::Closure& task,
    base::TimeDelta delay) {
  base::AutoLock lock(lock_);

  // Remove completed tasks.
  DCHECK(completed_tasks_.empty());
  task_graph_runner_.CollectCompletedTasks(namespace_token_, &completed_tasks_);

  cc::Task::Vector::iterator end = std::remove_if(
      tasks_.begin(), tasks_.end(), [this](const scoped_refptr<cc::Task>& e) {
        return std::find(this->completed_tasks_.begin(),
                         this->completed_tasks_.end(),
                         e) != this->completed_tasks_.end();
      });
  tasks_.erase(end, tasks_.end());

  tasks_.push_back(make_scoped_refptr(new ClosureTask(task)));
  graph_.Reset();
  for (const auto& graph_task : tasks_)
    graph_.nodes.push_back(cc::TaskGraph::Node(graph_task.get(), 0, 0));

  task_graph_runner_.ScheduleTasks(namespace_token_, &graph_);
  completed_tasks_.clear();
  return true;
}

bool RasterWorkerPool::RunsTasksOnCurrentThread() const {
  return true;
}

// Overridden from base::DelegateSimpleThread::Delegate:
void RasterWorkerPool::Run() {
  task_graph_runner_.Run();
}

scoped_refptr<base::SequencedTaskRunner>
RasterWorkerPool::CreateSequencedTaskRunner() {
  return new RasterWorkerPoolSequencedTaskRunner(&task_graph_runner_);
}

RasterWorkerPool::~RasterWorkerPool() {}

RasterWorkerPool::ClosureTask::ClosureTask(const base::Closure& closure)
    : closure_(closure) {}

// Overridden from cc::Task:
void RasterWorkerPool::ClosureTask::RunOnWorkerThread() {
  closure_.Run();
  closure_.Reset();
};

RasterWorkerPool::ClosureTask::~ClosureTask() {}

}  // namespace content