代码路径
所在代码位置：src/common/WorkQueue.cc
线程池功能描述
线程池主要成员
class ThreadPool : public md_config_obs_t
{
unsigned _num_threads; //构造线程池时指定的线程数量
std::vector<WorkQueue_*> work_queues; //待处理队列
std::set<WorkThread*> _threads; //线程对象集合
std::list<WorkThread*> _old_threads; //待join的线程集合
}
线程池函数逻辑
- start()
void ThreadPool::start_threads()
{
ceph_assert(ceph_mutex_is_locked(_lock));
while (_threads.size() < _num_threads) { //1. 线程数量到达配置线程数量之前，不断创建新线程对象
WorkThread *wt = new WorkThread(this);
ldout(cct, 10) << "start_threads creating and starting " << wt << dendl;
_threads.insert(wt); //2. 放入到线程池集合中
wt->create(thread_name.c_str()); //3. 创建pthread线程，并不断运行 WorkThread->pool->worker()
// _threads中的线程从work_queues中竞争待处理队列
}
}
- worker()
线程池核心运行函数
void ThreadPool::worker(WorkThread *wt)
{
std::unique_lock ul(_lock);
while (!_stop) {
// manage dynamic thread pool
join_old_threads(); // 1. join _old_threads集合中的线程
if (_threads.size() > _num_threads) {
_threads.erase(wt);
_old_threads.push_back(wt);
break;
}
if (!_pause && !work_queues.empty()) {
WorkQueue_* wq;
int tries = 2 * work_queues.size();
bool did = false;
while (tries--) {
next_work_queue %= work_queues.size();
wq = work_queues[next_work_queue++]; // 2. 某个线程从work_queues中竞争到一个wq
void *item = wq->_void_dequeue(); // 3. 从当前work_queue中取出一个item处理
if (item) {
processing++;
ldout(cct,12) << "worker wq " << wq->name << " start processing " << item
<< " (" << processing << " active)" << dendl;
ul.unlock();
...
wq->_void_process(item, tp_handle); // 4. 调用队列处理函数_void_process，放锁后执行，因此存在并发
ul.lock();
wq->_void_process_finish(item); // 5. 调用队列处理finish函数_void_process_finish，不存在并发
processing--;
ldout(cct,15) << "worker wq " << wq->name << " done processing " << item
<< " (" << processing << " active)" << dendl;
if (_pause || _draining)
_wait_cond.notify_all(); // 6. 唤醒等待的线程
did = true;
break;
}
}
if (did)
continue;
}
}
}
- pause(): 暂停线程池处理
- unpause()： 继续线程池处理
- drain(): 排空work_queue
- stop(): join所有线程池中线程， 清空work_queue_队列（不执行，直接放弃）
队列结构
虚基类WorkQueue_
struct WorkQueue_ {
std::string name;
time_t timeout_interval, suicide_interval;
WorkQueue_(std::string n, time_t ti, time_t sti)
: name(std::move(n)), timeout_interval(ti), suicide_interval(sti)
{ }
virtual ~WorkQueue_() {}
/// Remove all work items from the queue.
virtual void _clear() = 0;
/// Check whether there is anything to do.
virtual bool _empty() = 0;
/// Get the next work item to process.
virtual void *_void_dequeue() = 0; //取出待处理的items
/** @brief Process the work item.
* This function will be called several times in parallel
* and must therefore be thread-safe. */
virtual void _void_process(void *item, TPHandle &handle) = 0;
/** @brief Synchronously finish processing a work item.
* This function is called after _void_process with the global thread pool lock held,
* so at most one copy will execute simultaneously for a given thread pool.
* It can be used for non-thread-safe finalization. */
virtual void _void_process_finish(void *) = 0;
};
四类work_queue
- BatchWorkQueue
- 每次可以取出多个待处理item
- 该WorkQueued的item存放容器需要自行定义
- 需要自行实现如下接口（主要函数）：
virtual void _dequeue(std::list<T*> *) = 0: 如何从队列中work_queue中拿出itemsvirtual bool _enqueue(T *) = 0: 入队列接口virtual void _process(const std::list<T*> &items, TPHandle &handle) = 0: 批处理接口
- WorkQueueVal
- 适用于处理原始值类型或者小对象
- 将T类型item的值存储队列
- 存储T类型值的容器需要自行实现
- 处理缓存容器已经实现，用于存在中间值：
- std::list to_process; //待处理list， 从放入_void_dequeue()拿出的元素U，每次存入一个
- std::list to_finish; //_void_process_finish会处理该list中的元素，每次处理一个
- 需要自行实现如下接口：
bool _empty() override = 0: 判断容器非空virtual void _enqueue(T) = 0;: 入队列接口virtual void _process(U u, TPHandle &) = 0;: 处理元素U的函数
- WorkQueue
- 适用于处理大对象或者动态申请内存的对象
- 存储容器需要自行实现
- 需要自行实现如下接口：
virtual bool _enqueue(T *) = 0;: 入workqueue接口virtual T *_dequeue() = 0;： 取work_queue item接口virtual void _process(T *t, TPHandle &) = 0;: item处理接口
- PointerWQ
- 适用于处理大对象或者动态申请内存的对象，比WorkQueue更加方便，但是没有WorkQueue抽象
- 存储容器已经实现：
std::list<T *> m_items - 只需要实现
virtual void process(T *item) = 0;, 用于item处理
可直接使用的两种实现
-
**class GenContextWQ **: public ThreadPool::WorkQueueVal<GenContextThreadPool::TPHandle&*>
-
class ContextWQ : public ThreadPool::PointerWQ
应用举例
创建队列结构
class New_WQ : public ThreadPool::PointerWQ<Context>
{
public:
New_WQ(const std::string &name, time_t ti, ThreadPool *tp)
: ThreadPool::PointerWQ<Context>(name, ti, 0, tp) {
this->register_work_queue();
}
void process(Context *fin) override;
};
void New_WQ::process(Context *fin)
{
fin->complete(0);
}
启动线程池
1. 创建ThreadPool
thread_pool = new ThreadPool(cct, "thread_pool", "daemon_tp", g_conf()->rep_thread_pool_nr);
thread_pool->start();
2. 创建队列
work_queue = new New_WQ("daemon", 60, thread_pool);
投递任务
Context *ctx = new Test_TheadPool();
work_queue->queue(ctx);
销毁线程池
work_queue->drain();
delete work_queue;
work_queue = nullptr;
thread_pool->stop();
delete thread_pool;
thread_pool = nullptr;