测量程序的运行时间

问题描述

我需要一个工具来测量程序的运行时间，比如 gprof.但是gprof的分辨率不够好(约0.01秒).oprofile 似乎可以做到，我将尝试学习如何获取有关时间信息的数据，但我不能.

I need a tool to measure a program's running time, like gprof. But the resolution of gprof is not good enough (about 0.01 second). oprofile seems can do it, I will try to learn how to get the data about the time info, but I can't.

那么，谁能告诉我怎么做的步骤，或者谁知道其他工具可以做同样的事情?

So, who can tell me the steps how to do it, or anyone knows other tool can do the same thing?

推荐答案

在高分辨率下测量整个程序执行的运行时间很少有用；在分析事物时，您通常不想包含太多的开销.

Measuring runtime over a whole program's execution is seldom useful with high resolution; there's too much overhead that you generally don't want to include when you're profiling things.

通常最好仅测量某些关键路径的执行时间，即使如此，多次重复执行该路径通常也是一个好主意，以提高计时准确性.

It's often better to measure the execution time of some critical path only, and even then it's often a good idea to repeat the execution of that path many times, to improve timing accuracy.

在 Linux/POSIX 系统下，gettimeofday()通常用于这种计时，它具有微秒级精度:

Under Linux/POSIX systems, gettimeofday() is often used for such timing, it has microsecond precision:

#include <sys/time.h>
#include <time.h>
#include <stdio.h>

int main(void)
{
  struct timeval then, now;
  int i;

  gettimeofday(&then, NULL);
  for(i = 0; i < 100000; i++)
    my_interesting_function();
  gettimeofday(&now, NULL);

  printf("Did %d executions in %.3g seconds\n", i, now.tv_sec - then.tv_sec + 1e-6 * (now.tv_usec - then.tv_usec));

  return 0;
}

以上假设 my_interesting_function() 是您要测量其性能的函数.当然根据函数的实际运行时间调整重复次数.

The above assumes that my_interesting_function() is the function whose performance you want to measure. Of course tweak the number of repetitions depending on the actual runtime of the function.

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