thread_pool.h revision 7940e44f4517de5e2634a7e07d58d0fb26160513 
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_SRC_THREAD_POOL_H_
18#define ART_SRC_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 {
33public:
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  friend class ThreadPool;
59  DISALLOW_COPY_AND_ASSIGN(ThreadPoolWorker);
60};
61
62class ThreadPool {
63 public:
64  // Returns the number of threads in the thread pool.
65  size_t GetThreadCount() const {
66    return threads_.size();
67  }
68
69  // Broadcast to the workers and tell them to empty out the work queue.
70  void StartWorkers(Thread* self);
71
72  // Do not allow workers to grab any new tasks.
73  void StopWorkers(Thread* self);
74
75  // Add a new task, the first available started worker will process it. Does not delete the task
76  // after running it, it is the caller's responsibility.
77  void AddTask(Thread* self, Task* task);
78
79  ThreadPool(size_t num_threads);
80  virtual ~ThreadPool();
81
82  // Wait for all tasks currently on queue to get completed.
83  void Wait(Thread* self, bool do_work, bool may_hold_locks);
84
85  size_t GetTaskCount(Thread* self);
86
87  // Returns the total amount of workers waited for tasks.
88  uint64_t GetWaitTime() const {
89    return total_wait_time_;
90  }
91
92 protected:
93  // Get a task to run, blocks if there are no tasks left
94  virtual Task* GetTask(Thread* self);
95
96  // Try to get a task, returning NULL if there is none available.
97  Task* TryGetTask(Thread* self);
98  Task* TryGetTaskLocked(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_);
99
100  // Are we shutting down?
101  bool IsShuttingDown() const EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_) {
102    return shutting_down_;
103  }
104
105  Mutex task_queue_lock_;
106  ConditionVariable task_queue_condition_ GUARDED_BY(task_queue_lock_);
107  ConditionVariable completion_condition_ GUARDED_BY(task_queue_lock_);
108  volatile bool started_ GUARDED_BY(task_queue_lock_);
109  volatile bool shutting_down_ GUARDED_BY(task_queue_lock_);
110  // How many worker threads are waiting on the condition.
111  volatile size_t waiting_count_ GUARDED_BY(task_queue_lock_);
112  std::deque<Task*> tasks_ GUARDED_BY(task_queue_lock_);
113  // TODO: make this immutable/const?
114  std::vector<ThreadPoolWorker*> threads_;
115  // Work balance detection.
116  uint64_t start_time_ GUARDED_BY(task_queue_lock_);
117  uint64_t total_wait_time_;
118  Barrier creation_barier_;
119
120  friend class ThreadPoolWorker;
121  friend class WorkStealingWorker;
122  DISALLOW_COPY_AND_ASSIGN(ThreadPool);
123};
124
125class WorkStealingTask : public Task {
126 public:
127  WorkStealingTask() : ref_count_(0) {
128
129  }
130
131  size_t GetRefCount() const {
132    return ref_count_;
133  }
134
135  virtual void StealFrom(Thread* self, WorkStealingTask* source) = 0;
136
137 private:
138  // How many people are referencing this task.
139  size_t ref_count_;
140
141  friend class WorkStealingWorker;
142};
143
144class WorkStealingWorker : public ThreadPoolWorker {
145 public:
146  virtual ~WorkStealingWorker();
147
148  bool IsRunningTask() const {
149    return task_ != NULL;
150  }
151
152 protected:
153  WorkStealingTask* task_;
154
155  WorkStealingWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
156  virtual void Run();
157
158  friend class WorkStealingThreadPool;
159  DISALLOW_COPY_AND_ASSIGN(WorkStealingWorker);
160};
161
162class WorkStealingThreadPool : public ThreadPool {
163 public:
164  WorkStealingThreadPool(size_t num_threads);
165  virtual ~WorkStealingThreadPool();
166
167 private:
168  Mutex work_steal_lock_;
169  // Which thread we are stealing from (round robin).
170  size_t steal_index_;
171
172  // Find a task to steal from
173  WorkStealingTask* FindTaskToStealFrom(Thread* self) EXCLUSIVE_LOCKS_REQUIRED(work_steal_lock_);
174
175  friend class WorkStealingWorker;
176};
177
178}  // namespace art
179
180#endif  // ART_SRC_THREAD_POOL_H_
181