Add thread pool class

Added a thread pool class loosely based on google3 code.

Modified the compiler to have a single thread pool instead of creating new threads in ForAll.

Moved barrier to be in top level directory as it is not GC specific code.

Performance Timings:

Reference:
boot.oat: 14.306596s
time mm oat-target:
real    2m33.748s
user    10m23.190s
sys 5m54.140s

Thread pool:
boot.oat: 13.111049s
time mm oat-target:
real    2m29.372s
user    10m3.130s
sys 5m46.290s

The speed increase is probably just noise.

Change-Id: If3c1280cbaa4c7e4361127d064ac744ea12cdf49

1 files changed, 103 insertions, 0 deletions

diff --git a/src/thread_pool.h b/src/thread_pool.h
new file mode 100644
index 0000000000..22e30b71fe
--- /dev/null
+++ b/src/thread_pool.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_SRC_THREAD_POOL_H_
+#define ART_SRC_THREAD_POOL_H_
+
+#include <deque>
+#include <vector>
+
+#include "locks.h"
+#include "../src/mutex.h"
+
+namespace art {
+
+class Closure;
+class ThreadPool;
+
+class ThreadPoolWorker {
+ public:
+  static const size_t kDefaultStackSize = 1 * MB;
+
+  size_t GetStackSize() const {
+    return stack_size_;
+  }
+
+  virtual ~ThreadPoolWorker();
+
+ private:
+  ThreadPoolWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
+  static void* Callback(void* arg) LOCKS_EXCLUDED(Locks::mutator_lock_);
+  void Run();
+
+  ThreadPool* thread_pool_;
+  const std::string name_;
+  const size_t stack_size_;
+  pthread_t pthread_;
+  pthread_attr_t attr;
+
+  friend class ThreadPool;
+  DISALLOW_COPY_AND_ASSIGN(ThreadPoolWorker);
+};
+
+class ThreadPool {
+ public:
+  // Returns the number of threads in the thread pool.
+  size_t GetThreadCount() const {
+    return threads_.size();
+  }
+
+  // Broadcast to the workers and tell them to empty out the work queue.
+  void StartWorkers(Thread* self);
+
+  // Do not allow workers to grab any new tasks.
+  void StopWorkers(Thread* self);
+
+  // Add a new task, the first available started worker will process it. Does not delete the task
+  // after running it, it is the caller's responsibility.
+  void AddTask(Thread* self, Closure* task);
+
+  ThreadPool(size_t num_threads);
+  virtual ~ThreadPool();
+
+  // Wait for all tasks currently on queue to get completed.
+  void Wait(Thread* self);
+
+ private:
+  // Add a new task.
+  void AddThread(size_t stack_size);
+
+  // Get a task to run, blocks if there are no tasks left
+  Closure* GetTask(Thread* self);
+
+  Mutex task_queue_lock_;
+  ConditionVariable task_queue_condition_ GUARDED_BY(task_queue_lock_);
+  ConditionVariable completion_condition_ GUARDED_BY(task_queue_lock_);
+  volatile bool started_ GUARDED_BY(task_queue_lock_);
+  volatile bool shutting_down_ GUARDED_BY(task_queue_lock_);
+  // How many worker threads are waiting on the condition.
+  volatile size_t waiting_count_ GUARDED_BY(task_queue_lock_);
+  std::deque<Closure*> tasks_ GUARDED_BY(task_queue_lock_);
+  // TODO: make this immutable/const?
+  std::vector<ThreadPoolWorker*> threads_;
+
+  friend class ThreadPoolWorker;
+  DISALLOW_COPY_AND_ASSIGN(ThreadPool);
+};
+
+}  // namespace art
+
+#endif  // ART_SRC_THREAD_POOL_H_