r - R system.time(exp) 输出中测量的 'user' 和 'system' 时间是多少？

Question

我正在使用 system.time(expression) 来测量 R 函数的执行时间。

我获得的调用输出

system.time(myfunction())

是:

    user  system elapsed   
  117.36    5.65  127.86

“用户”和“系统”衡量什么？

Answer 1

我读过的关于用户和系统运行时间之间差异的最清晰的解释由William Dunlap on [R-help]提供。 :

"User CPU time" gives the CPU time spent by the current process (i.e., the current R session) and "system CPU time" gives the CPU time spent by the kernel (the operating system) on behalf of the current process. The operating system is used for things like opening files, doing input or output, starting other processes, and looking at the system clock: operations that involve resources that many processes must share.

虽然 ?proc.time 返回类似的内容，但这个描述对我来说更容易理解。