问题描述

我对在 Windows 中使用 C++ 测量精确到纳秒的特定时间点很感兴趣.这可能吗?如果不是，是否可以至少以微秒为单位获得特定时间?任何库都应该这样做，除非我认为托管代码是可能的.谢谢

I'm interested in measuring a specific point in time down to the nanosecond using C++ in Windows. Is this possible? If it isn't, is it possible to get the specific time in microseconds at least?. Any library should do, unless I suppose it's possible with managed code. thanks

推荐答案

如果您有一个线程应用程序在多核计算机上运行 QueryPerformanceCounter 可以(并将)根据代码的内核返回不同的值正在执行.请参阅这篇 MSDN 文章.(rdtsc 也有同样的问题)

If you have a threaded application running on a multicore computer QueryPerformanceCounter can (and will) return different values depending on which core the code is executing on. See this MSDN article. (rdtsc has the same problem)

这不仅仅是一个理论问题；我们在我们的应用程序中遇到了它，并且不得不得出结论，唯一可靠的时间源是 timeGetTime ，它只有 ms 精度(幸运的是，在我们的例子中已经足够了).我们还尝试为我们的线程固定线程关联，以保证每个线程始终从 QueryPerformanceCounter 获得一致的值，这有效，但它绝对降低了应用程序的性能.

This is not just a theoretical problem; we ran into it with our application and had to conclude that the only reliable time source is timeGetTime which only has ms precision (which fortunately was sufficient in our case). We also tried fixating the thread affinity for our threads to guarantee that each thread always got a consistent value from QueryPerformanceCounter, this worked but it absolutely killed the performance in the application.

总而言之，Windows 上没有一个可靠计时器可以用于以微秒精度计时(至少在多核计算机上运行时不会).

To sum things up there isn't a reliable timer on windows that can be used to time thing with micro second precision (at least not when running on a multicore computer).

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