#include <time.h>
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>

static inline uint64_t
rdtsc(void)
{
        uint64_t rv;

        __asm __volatile("rdtsc" : "=A" (rv));
        return (rv);
}


int main(int argc, char *argv[])
{
	uint64_t begin, end, sum = 0, used = 0, unused = 0;
	int i, min = (1<<30)-1, max = 0, diff, avg;
	printf("Estimating interval "); 
	for (i = 0; i < 101; ++i)
	{
		begin = rdtsc();
		usleep(1);
		end = rdtsc();
		if (i > 0)
		{
			diff = end - begin;
			if (diff > max)
				max = diff;
			if (diff < min)
				min = diff;
			sum += diff;
		}
	}
	avg = sum / 100;
	printf(" min %d max %d avg %d\n", min, max, avg);

	i = 0;
	for (;;)
	{
		begin = rdtsc();
		if ((++i % 500) == 0)
		{
			printf("Using about %d%% of the CPU\r",
			    (int)(used * 100 / (used + unused)));
			fflush(stdout);
		}
		end = begin + avg * 15 / 100;
		while (rdtsc() < end)
			;
		end = rdtsc();
		used += end - begin;
		begin = end;
		usleep(1);
		end = rdtsc();
		unused += end - begin;
	}
	return (0);
}