Poco::ThreadPool
Poco::ThreadPool提供线程池功能，减少线程的创建和销毁所带来的开销，适合在服务器上应用。创建线程池时指定最少运行线程数和线程池的最大容量，若不指定则采用默认值，取2和16 。线程池的实现机制：有一部分线程始终处于运行状态，但阻塞在Event的wait调用上，所以处于休眠状态，开销并不大。如果我们需要一个线程来运行一段代码（在Poco中，用Runnable的子类表示一个target），则从线程池中去除一个线程，并将这段代码赋给它，并触发Event。然后线程就继续运行了。
活动图
void ThreadPoolTest::testThreadPool(){ThreadPool pool(2, 3, 3);assert (pool.allocated() == 2);assert (pool.used() == 0);assert (pool.capacity() == 3);assert (pool.available() == 3);pool.addCapacity(1);assert (pool.allocated() == 2);assert (pool.used() == 0);assert (pool.capacity() == 4);assert (pool.available() == 4);RunnableAdapter<ThreadPoolTest> ra(*this, &ThreadPoolTest::hello);pool.start(ra);assert (pool.allocated() == 2);assert (pool.used() == 1);assert (pool.capacity() == 4);assert (pool.available() == 3);pool.start(ra);assert (pool.allocated() == 2);assert (pool.used() == 2);assert (pool.capacity() == 4);assert (pool.available() == 2);pool.start(ra);assert (pool.allocated() == 3);assert (pool.used() == 3);assert (pool.capacity() == 4);assert (pool.available() == 1);pool.start(ra);assert (pool.allocated() == 4);assert (pool.used() == 4);assert (pool.capacity() == 4);assert (pool.available() == 0);}线程池的内存策略有点像MemoryPool，请参加http://blog.csdn.net/fym0121/article/details/7840801