Short program for generating load to test AWS micro instances

testmicro.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <math.h>

long int getMicroseconds();

int main(int argc, char **argv) {
  int percentage;
  int dutycycle;
  int activetime;
  int testduration = 1000000000;

  long int nextcycle;
  long int idle;
  long int starttime;
  long int now;
  long int t = 0;

  int i;
  int n=0;
  double d;
  double result = 0;

  if (argc != 3 && argc != 4) {
    printf("Usage:   %s <CPU utilization 0...100%%> <duty cycle ms> [test time s]\n", argv[0]);
    printf("Example: %s 50 10 180  # 50%% utilization at 10 ms duty cycle for 3 mins\n", argv[0]);
    exit(1);
  }

  percentage = atoi(argv[1]);
  dutycycle = atoi(argv[2]) * 1000;
  activetime = (percentage * dutycycle)/100;
  if (argc >= 4) {
    testduration = atoi(argv[3]) * 1000000;
  }

  starttime = getMicroseconds();
  nextcycle = getMicroseconds() + dutycycle;

  while (t < testduration) {
    // Active time
    idle = getMicroseconds() + activetime;
    n = 0;
    d = 100;
    while (getMicroseconds() < idle) {
      for (i=0; i<10000; i++) {
	d = sqrt(d) + 100;
      }
      n++;
    }
    result += d;

    // Idle time
    now = getMicroseconds();
    if (now < nextcycle) {
      while (getMicroseconds() < nextcycle) {
	usleep(nextcycle - getMicroseconds());
      }
      nextcycle = nextcycle + dutycycle;
    } else {
      printf("Missed next cycle by %d us\n", (int)(now - nextcycle));
      nextcycle = getMicroseconds() + dutycycle;
    }

    // Report result
    t = getMicroseconds() - starttime;
    printf("t = %d ms:  %d rounds\n", (int)(t/1000), n);
    fflush(stdout);
  }
  
  // Ensure the math operations cannot be optimized away
  if (d < 0) {
    printf("%.f\n", d);
  }

  return 0;
}

long int getMicroseconds() {
  struct timeval tv;
  gettimeofday(&tv, NULL);
  return ((long int)tv.tv_sec)*1000000 + tv.tv_usec;
}