对于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的计算密集型+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：一个是多任务处理下运行，另一种是在多线程运行

。

我发现性能多的多处理好。我读别的地方（但我不记得站点）。

其中规定，原因是在多线程，它们是激战的单条内存流水线和I / O管道，相对于多处理器使得性能更差

不过，我找不到那篇文章了。我想知道，直到今天，下面是否仍然适用？

  

在Windows中，具有算法
  多处理下code运行，有一个高
  机会表现会
  比多线程更好。

解决方案

这取决于有多少不同的线程或进程（我将使用通用术语任务对他们俩的），需要沟通，特别是共享内存：这很简单，廉价，​​快速的线程，但不是所有的过程，因此，如果有很多这是怎么回事，我敢打赌，流程的绩效是的不的将击败线程。

此外，过程（特别是在Windows上）的重上手，所以如果有很多的任务启动出现，再一次线程可以很容易地在性能方面击败流程。

接下来，你可以有超线程的CPU，它可以运行（至少）上的一个核心两个线程非常迅速 - 但是，没有过程（因为超线程线程不能使用不同的地址空间来） - 另一起案件中，线程可以赢得的性能，明智的。

如果没有这些因素的适用，那么比赛应该没有比一条领带更好，反正。

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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