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看到论坛上有人问python多线程和C++多线程的区别？
暖神是这样回答的：
Python有Global Interpreter Lock，所以嘛……你懂的。
C++11开始才有多线程，使用共享内存方式的线程间通信，有低级的atomic operation和memory order，以及高级的lock, condition的，却没有提供消息队列。
然后，就去找GIL(Global Interpreter Lock)的定义，下面有一个定义，wiki的定义是这样的。在stackoverflow上看到了另外一个更通俗的解释：
Suppose you have multiple threads which don‘t really touch each other‘s data. Those should execute as independently as possible. If you have a "global lock" which you need to acquire in order to (say) call a function, that can end up as a bottleneck. You can wind up not getting much benefit from having multiple threads in the first place.
To put it into a real world analogy: imagine 100 developers working at a company with only a single coffee mug. Most of the developers would spend their time waiting for coffee instead of coding.
None of this is Python-specific - I don‘t know the details of what Python needed a GIL for in the first place. However, hopefully it‘s given you a better idea of the general concept.
大概明白了一个基本的意思：GIL（全局解释器锁）会序列化线程访问，所以在加了GIL锁的情况下，多线程的优势和特点并不能真正发挥出来。甚至没有单线程跑得快，因为在acquire和relea锁的时候会执行额外的线程调度指令。这个GIL只在CPython中有，方便加载C的extension，Jython和ironpython里面是木有的。所以，在python里面应该用颗粒度更小的锁？
说到C++，上文暖神说到atomic operation，就是原子锁啦，具体的在这里有一个清晰的说明，atomic是一个好东西。。。。至于memory order，表示没看懂。。。还是老老实实的取用mutex吧。。。。。。
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原文地址：http://www.cnblogs.com/kzcdqbz/p/4741017.html
