c++ - 如何在多核机器上解释 boost::timer::cpu_timer 的输出？

Question

我使用 boost::timer::cpu_timer 来衡量我的应用程序中某些算法的性能。示例输出如下所示:

Algo1 duration: 6.755457s wall, 12.963683s user + 1.294808s system = 14.258491s CPU (211.1%)

来自 boost cpu_timer 文档:

The output of this program will look something like this:

5.713010s wall, 5.709637s user + 0.000000s system = 5.709637s CPU (99.9%)

In other words, this program ran in 5.713010 seconds as would be measured by a clock on the wall, the operating system charged it for 5.709637 seconds of user CPU time and 0 seconds of system CPU time, the total of these two was 5.709637, and that represented 99.9 percent of the wall clock time.

我获得的值 (211.1%) 是什么意思，是否意味着我的算法执行涉及两个以上的核心？

用户 CPU 时间 和 系统 CPU 时间 是什么意思？

Answer 1

What does the value I obtained mean (211.1%), does it mean that more than two cores were involved in execution of my algorithm ?

这意味着该程序使用的 CPU 时间是 wall time 的两倍多一点。为此，它必须在至少三个内核上运行一段时间。

What is the meaning of user CPU time and system CPU time ?

用户CPU时间是CPU运行用户代码的时间。系统CPU时间是CPU运行系统代码的时间。当您调用系统函数时，例如从文件读取的函数，您会从运行用户代码切换到运行系统代码，直到该函数返回。