多线程和多进程的性能差异 [英] Performance difference for multi-thread and multi-process

问题描述

几年前，在Windows环境下，我做了一些测试，通过让CPU计算密集型+内存访问密集型+I/O访问密集型应用程序运行多个实例.我开发了两个版本:一个在多处理下运行，另一个在多线程下运行.

我发现多处理的性能要好得多.我在别处读过(但我不记得那个网站了).

其中说明原因是在多线程下，他们在争夺"单个内存管道和I/O管道，这使得性能比多处理更差>

但是，我再也找不到那篇文章了.我想知道，直到今天，以下是否仍然适用?

<块引用>

在Windows中，有算法代码在多处理下运行，有很高的演出的机会比多线程更好.

解决方案

这取决于各种线程或进程(我将使用统称任务"来表示它们)需要进行多少通信，尤其是通过共享内存:对于线程来说这很容易、便宜且快速，但对于进程来说根本不是，所以，如果很多事情正在发生，我敢打赌进程的性能不会击败线程'.

此外，进程(尤其是在 Windows 上)启动起来更繁重"，因此如果发生大量任务启动"，线程在性能方面很容易再次击败进程.

接下来，您可以拥有具有超线程"功能的 CPU，它可以(至少)非常快速地在一个内核上运行两个线程——但不是进程(因为超线程"线程不能使用不同的地址空间)——线程可以在性能方面获胜的另一种情况.

如果这些考虑都不适用，那么无论如何比赛应该不会比平局好.

A few years ago, in the Windows environment, I did some testing, by letting multiple instances of CPU computation intensive + memory access intensive + I/O access intensive application run. I developed 2 versions: One is running under multi-processing, another is running under multi-threading.

I found that the performance is much better for multi-processing. I read somewhere else (but I can't remember the site).

Which states that the reason is that under multi-threading, they are "fighting" for a single memory pipeline and I/O pipeline, which makes the performance worse compared to multi-processing

However, I can't find that article anymore. I was wondering, till today, whether the below still hold true?

In Windows, having the algorithm code run under multi-processing, there is a high chance that the performance will be better than multi-threading.

解决方案

It depends on how much the various threads or processes (I'll be using the collective term "tasks" for both of them) need to communicate, especially by sharing memory: that's easy, cheap and fast for threads, but not at all for processes, so, if a lot of it is going on, I bet processes' performance is not going to beat threads'.

Also, processes (esp. on Windows) are "heavier" to get started, so if a lot of "task starts" occur, again threads can easily beat processes in terms of performance.

Next, you can have CPUs with "hyperthreading", which can run (at least) two threads on a core very rapidly -- but, not processes (since the "hyperthreaded" threads cannot be using distinct address spaces) -- yet another case in which threads can win performance-wise.

If none of these considerations apply, then the race should be no better than a tie, anyway.

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