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/*
* 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_RUNTIME_THREAD_POOL_H_
#define ART_RUNTIME_THREAD_POOL_H_
#include <deque>
#include <vector>
#include "barrier.h"
#include "base/mutex.h"
#include "mem_map.h"
namespace art {
class ThreadPool;
class Closure {
public:
virtual ~Closure() { }
virtual void Run(Thread* self) = 0;
};
class Task : public Closure {
public:
// Called after Closure::Run has been called.
virtual void Finalize() { }
};
class SelfDeletingTask : public Task {
public:
virtual ~SelfDeletingTask() { }
virtual void Finalize() {
delete this;
}
};
class ThreadPoolWorker {
public:
static const size_t kDefaultStackSize = 1 * MB;
size_t GetStackSize() const {
DCHECK(stack_.get() != nullptr);
return stack_->Size();
}
virtual ~ThreadPoolWorker();
protected:
ThreadPoolWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
static void* Callback(void* arg) LOCKS_EXCLUDED(Locks::mutator_lock_);
virtual void Run();
ThreadPool* const thread_pool_;
const std::string name_;
std::unique_ptr<MemMap> stack_;
pthread_t pthread_;
private:
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, Task* task);
explicit ThreadPool(const char* name, size_t num_threads);
virtual ~ThreadPool();
// Wait for all tasks currently on queue to get completed.
void Wait(Thread* self, bool do_work, bool may_hold_locks);
size_t GetTaskCount(Thread* self);
// Returns the total amount of workers waited for tasks.
uint64_t GetWaitTime() const {
return total_wait_time_;
}
// Provides a way to bound the maximum number of worker threads, threads must be less the the
// thread count of the thread pool.
void SetMaxActiveWorkers(size_t threads);
protected:
// get a task to run, blocks if there are no tasks left
virtual Task* GetTask(Thread* self);
// Try to get a task, returning null if there is none available.
Task* TryGetTask(Thread* self);
Task* TryGetTaskLocked() EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_);
// Are we shutting down?
bool IsShuttingDown() const EXCLUSIVE_LOCKS_REQUIRED(task_queue_lock_) {
return shutting_down_;
}
const std::string name_;
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<Task*> tasks_ GUARDED_BY(task_queue_lock_);
// TODO: make this immutable/const?
std::vector<ThreadPoolWorker*> threads_;
// Work balance detection.
uint64_t start_time_ GUARDED_BY(task_queue_lock_);
uint64_t total_wait_time_;
Barrier creation_barier_;
size_t max_active_workers_ GUARDED_BY(task_queue_lock_);
private:
friend class ThreadPoolWorker;
friend class WorkStealingWorker;
DISALLOW_COPY_AND_ASSIGN(ThreadPool);
};
class WorkStealingTask : public Task {
public:
WorkStealingTask() : ref_count_(0) {}
size_t GetRefCount() const {
return ref_count_;
}
virtual void StealFrom(Thread* self, WorkStealingTask* source) = 0;
private:
// How many people are referencing this task.
size_t ref_count_;
friend class WorkStealingWorker;
};
class WorkStealingWorker : public ThreadPoolWorker {
public:
virtual ~WorkStealingWorker();
bool IsRunningTask() const {
return task_ != nullptr;
}
protected:
WorkStealingTask* task_;
WorkStealingWorker(ThreadPool* thread_pool, const std::string& name, size_t stack_size);
virtual void Run();
private:
friend class WorkStealingThreadPool;
DISALLOW_COPY_AND_ASSIGN(WorkStealingWorker);
};
class WorkStealingThreadPool : public ThreadPool {
public:
explicit WorkStealingThreadPool(const char* name, size_t num_threads);
virtual ~WorkStealingThreadPool();
private:
Mutex work_steal_lock_;
// Which thread we are stealing from (round robin).
size_t steal_index_;
// Find a task to steal from
WorkStealingTask* FindTaskToStealFrom() EXCLUSIVE_LOCKS_REQUIRED(work_steal_lock_);
friend class WorkStealingWorker;
};
} // namespace art
#endif // ART_RUNTIME_THREAD_POOL_H_
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