1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_THREAD_POOL_H_
18#define ART_RUNTIME_THREAD_POOL_H_
19
20#include <deque>
21#include <vector>
22
23#include "barrier.h"
24#include "base/mutex.h"
25#include "closure.h"
26#include "locks.h"
27
28namespace art {
29
30class ThreadPool;
31
32class Task : public Closure {
33 public:
34  // Called when references reaches 0.
35  virtual void Finalize() { }
36};
37
38class ThreadPoolWorker {
39 public:
40  static const size_t kDefaultStackSize = 1 * MB;
41
42  size_t GetStackSize() const {
43    return stack_size_;
44  }
45
46  virtual ~ThreadPoolWorker();
47
48 protected:
49  ThreadPoolWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
50  static void* Callback(void* arg) LOCKS_EXCLUDED(Locks::mutator_lock_);
51  virtual void Run();
52
53  ThreadPool* const thread_pool_;
54  const std::string name_;
55  const size_t stack_size_;
56  pthread_t pthread_;
57
58 private:
59  friend class ThreadPool;
60  DISALLOW_COPY_AND_ASSIGN(ThreadPoolWorker);
61};
62
63class ThreadPool {
64 public:
65  // Returns the number of threads in the thread pool.
66  size_t GetThreadCount() const {
67    return threads_.size();
68  }
69
70  // Broadcast to the workers and tell them to empty out the work queue.
71  void StartWorkers(Thread* self);
72
73  // Do not allow workers to grab any new tasks.
74  void StopWorkers(Thread* self);
75
76  // Add a new task, the first available started worker will process it. Does not delete the task
77  // after running it, it is the caller's responsibility.
78  void AddTask(Thread* self, Task* task);
79
80  explicit ThreadPool(size_t num_threads);
81  virtual ~ThreadPool();
82
83  // Wait for all tasks currently on queue to get completed.
84  void Wait(Thread* self, bool do_work, bool may_hold_locks);
85
86  size_t GetTaskCount(Thread* self);
87
88  // Returns the total amount of workers waited for tasks.
89  uint64_t GetWaitTime() const {
90    return total_wait_time_;
91  }
92
93  // Provides a way to bound the maximum number of worker threads, threads must be less the the
94  // thread count of the thread pool.
95  void SetMaxActiveWorkers(size_t threads);
96
97 protected:
98  // Get a task to run, blocks if there are no tasks left
99  virtual Task* GetTask(Thread* self);
100
101  // Try to get a task, returning NULL if there is none available.
102  Task* TryGetTask(Thread* self);
103  Task* TryGetTaskLocked(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_);
104
105  // Are we shutting down?
106  bool IsShuttingDown() const EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_) {
107    return shutting_down_;
108  }
109
110  Mutex task_queue_lock_;
111  ConditionVariable task_queue_condition_ GUARDED_BY(task_queue_lock_);
112  ConditionVariable completion_condition_ GUARDED_BY(task_queue_lock_);
113  volatile bool started_ GUARDED_BY(task_queue_lock_);
114  volatile bool shutting_down_ GUARDED_BY(task_queue_lock_);
115  // How many worker threads are waiting on the condition.
116  volatile size_t waiting_count_ GUARDED_BY(task_queue_lock_);
117  std::deque<Task*> tasks_ GUARDED_BY(task_queue_lock_);
118  // TODO: make this immutable/const?
119  std::vector<ThreadPoolWorker*> threads_;
120  // Work balance detection.
121  uint64_t start_time_ GUARDED_BY(task_queue_lock_);
122  uint64_t total_wait_time_;
123  Barrier creation_barier_;
124  size_t max_active_workers_ GUARDED_BY(task_queue_lock_);
125
126 private:
127  friend class ThreadPoolWorker;
128  friend class WorkStealingWorker;
129  DISALLOW_COPY_AND_ASSIGN(ThreadPool);
130};
131
132class WorkStealingTask : public Task {
133 public:
134  WorkStealingTask() : ref_count_(0) {}
135
136  size_t GetRefCount() const {
137    return ref_count_;
138  }
139
140  virtual void StealFrom(Thread* self, WorkStealingTask* source) = 0;
141
142 private:
143  // How many people are referencing this task.
144  size_t ref_count_;
145
146  friend class WorkStealingWorker;
147};
148
149class WorkStealingWorker : public ThreadPoolWorker {
150 public:
151  virtual ~WorkStealingWorker();
152
153  bool IsRunningTask() const {
154    return task_ != NULL;
155  }
156
157 protected:
158  WorkStealingTask* task_;
159
160  WorkStealingWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
161  virtual void Run();
162
163 private:
164  friend class WorkStealingThreadPool;
165  DISALLOW_COPY_AND_ASSIGN(WorkStealingWorker);
166};
167
168class WorkStealingThreadPool : public ThreadPool {
169 public:
170  explicit WorkStealingThreadPool(size_t num_threads);
171  virtual ~WorkStealingThreadPool();
172
173 private:
174  Mutex work_steal_lock_;
175  // Which thread we are stealing from (round robin).
176  size_t steal_index_;
177
178  // Find a task to steal from
179  WorkStealingTask* FindTaskToStealFrom(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(work_steal_lock_);
180
181  friend class WorkStealingWorker;
182};
183
184}  // namespace art
185
186#endif  // ART_RUNTIME_THREAD_POOL_H_
187