这取决于很多因素。进程比线程更重，启动和关闭成本更高。进程间通信(IPC)也比线程间通信更困难、更慢。

相反，进程比线程更安全，因为每个进程都运行在自己的虚拟地址空间中。如果一个进程崩溃或缓冲区溢出，它根本不会影响任何其他进程，而如果一个线程崩溃，它会关闭进程中的所有其他线程，如果一个线程缓冲区溢出，它会在所有线程中打开一个安全漏洞。

因此，如果应用程序的模块可以在很少通信的情况下独立运行，那么如果能够负担得起启动和关闭成本，则可能应该使用进程。IPC对性能的影响将是最小的，并且您在漏洞和安全漏洞方面会稍微安全一些。如果您需要获得或拥有大量共享数据(例如复杂的数据结构)，那么请使用线程。

其他人讨论了这些考虑因素。

也许重要的区别是，在Windows中，与线程相比，进程是沉重和昂贵的，而在Linux中，差异要小得多，所以等式在不同的点上平衡。

多线程是为受虐狂准备的。：）

If you are concerned about an environment where you are constantly creating threads/forks, perhaps like a web server handling requests, you can pre-fork processes, hundreds if necessary. Since they are Copy on Write and use the same memory until a write occurs, it's very fast. They can all block, listening on the same socket and the first one to accept an incoming TCP connection gets to run with it. With g++ you can also assign functions and variables to be closely placed in memory (hot segments) to ensure when you do write to memory, and cause an entire page to be copied at least subsequent write activity will occur on the same page. You really have to use a profiler to verify that kind of stuff but if you are concerned about performance, you should be doing that anyway.

Development time of threaded apps is 3x to 10x times longer due to the subtle interaction on shared objects, threading "gotchas" you didn't think of, and very hard to debug because you cannot reproduce thread interaction problems at will. You may have to do all sort of performance killing checks like having invariants in all your classes that are checked before and after every function and you halt the process and load the debugger if something isn't right. Most often it's embarrassing crashes that occur during production and you have to pore through a core dump trying to figure out which threads did what. Frankly, it's not worth the headache when forking processes is just as fast and implicitly thread safe unless you explicitly share something. At least with explicit sharing you know exactly where to look if a threading style problem occurs.

如果性能如此重要，那就增加另一台计算机和负载平衡。对于开发人员调试一个多线程应用程序的成本，即使是由一个有经验的多线程程序编写的应用程序，你可能会买4块40核的英特尔主板，每块都有64g内存。

That being said, there are asymmetric cases where parallel processing isn't appropriate, like, you want a foreground thread to accept user input and show button presses immediately, without waiting for some clunky back end GUI to keep up. Sexy use of threads where multiprocessing isn't geometrically appropriate. Many things like that just variables or pointers. They aren't "handles" that can be shared in a fork. You have to use threads. Even if you did fork, you'd be sharing the same resource and subject to threading style issues.

我不得不同意你所听到的。当我们对我们的集群(xhpl等)进行基准测试时，我们总是通过进程而不是线程获得明显更好的性能。< /轶事>

你的任务有多紧密耦合?

如果它们可以彼此独立，那么就使用流程。如果它们相互依赖，则使用线程。这样，您就可以终止并重新启动坏进程，而不会影响其他任务的操作。

从前有Unix，在这个好的旧Unix中，进程有很多开销，所以一些聪明的人所做的是创建线程，这些线程将与父进程共享相同的地址空间，他们只需要减少上下文切换，这将使上下文切换更有效。

在当代的Linux (2.6.x)中，进程的上下文切换和线程的上下文切换在性能上没有太大的区别(只有MMU的东西对线程来说是额外的)。 共享地址空间存在问题，这意味着线程中的错误指针可能破坏同一地址空间中的父进程或另一个线程的内存。

一个进程受到MMU的保护，所以一个错误的指针只会导致一个信号11，而不会损坏。

我通常会使用进程(在Linux中没有太多的上下文切换开销，但是由于MMU的内存保护)，但是如果我需要一个实时调度器类，则会使用pthreads，这完全是另一回事。

为什么你认为线程在Linux上有这么大的性能提升?你有这方面的数据吗，还是说这只是一个神话?