CPU最大线程数 [英] Maximum number of threads CPU

问题描述

这与处理器的线程有什么关系?例如，英特尔i5具有四个内核和四个线程.

What does this have to do with the threads of the processor? for example, an Intel i5 has four cores and four threads.

我们的程序中可以使用多少个线程?例如在C ++中使用std :: thread(STL)?

How many threads can we use in our program? for example using std :: thread (STL) in C ++?

一个程序的8个线程是大线程还是少线程?

is 8 threads a big or low number of threads for a program?

推荐答案

这确实取决于.根据经验，将线程数限制为接近内核数(否则，您可能有太多 std::thread::hardware_concurrency() 作为提示.通常，您使用线程池来组织程序.

It really depends. As a rule of thumb, limit the number of threads to something close to the number of cores (otherwise you might have too much context switchs). You might use std::thread::hardware_concurrency() as a hint. Often, you organize your program with a thread pool.

但是，真正重要的是 active 线程的数量.有些程序具有数百个线程，但它们的组织方式是这样的，以便在给定的瞬间它们只有少数处于活动状态(即可运行)，而大多数处于空闲状态(等待IO，某些互斥量或条件变量).

However, what really matters is the number of active threads. Some programs have hundreds of threads but are organized so that only a few of them are active (i.e. runnable) at any given instant, and most of them being idle (waiting for IO, or for some mutex or condition variable).

请注意，线程是非常重的资源(特别是因为它具有自己的调用堆栈，通常至少为一个兆字节).因此，不要太多(因此，除非您有一台非常强大且扩展的计算机，否则拥有数千个线程通常是不合理的.)

Be aware that a thread is a quite heavy resource (in particular because it has its own call stack, usually at least a megabyte). So don't have too many of them (hence, having thousands of threads is generally unreasonable, unless you have a very powerful and expansive computer).

英特尔超线程技术通常令人失望.您可能不想在具有4个核心和8个超线程的Intel处理器上拥有8个活动线程.您需要进行基准测试，但是在这种情况下，您可能会预期性能会有所下降(也许拥有4个或6个活动线程会使您的整体性能更好).

The Intel hyper-threading technology is often disappointing. You probably don't want to have 8 active threads on an Intel processor with 4 cores and 8 hyperthreads. You need to benchmark, but you should expect some bad performance in such case (perhaps having 4 or 6 active threads would make your overall performance better).

线程是 操作系统:三件简单的书 了解有关操作系统的更多信息.

Threads are an abstraction provided and managed by the operating system. So read Operating Systems: Three Easy Pieces to understand more about OSes.

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