CP.41: Minimize thread creation and destruction
CP.41:尽量回避线程的生成和销毁处理
Reason（原因）
Thread creation is expensive.
创建线程代价高昂。
Example（示例）
代码语言：javascript复制void worker(Message m)
{
// process
}
void dispatcher(istream& is)
{
for (Message m; is >> m; )
run_list.push_back(new thread(worker, m));
}
This spawns a thread per message, and the run_list is presumably managed to destroy those tasks once they are finished.
Instead, we could have a set of pre-created worker threads processing the messages
代码中为每个消息生成一个线程，而且run_list很可能准备在任务结束时销毁它们。
作为改善，我们可以准备一组事先生成的工作线程来处理这些消息。
代码语言：javascript复制Sync_queue<Message> work;
void dispatcher(istream& is)
{
for (Message m; is >> m; )
work.put(m);
}
void worker()
{
for (Message m; m = work.get(); ) {
// process
}
}
void workers() // set up worker threads (specifically 4 worker threads)
{
joining_thread w1 {worker};
joining_thread w2 {worker};
joining_thread w3 {worker};
joining_thread w4 {worker};
}Note（注意）
If your system has a good thread pool, use it. If your system has a good message queue, use it.
如果你的系统包含一个优秀的线程池，使用它。如果你的系统包含一个优秀的消息队列，使用它。
Enforcement（实施建议）
???
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#cp41-minimize-thread-creation-and-destruction
