入职Oracle 以后想着把之前写过的《编程之美》中控制CPU使用率曲线的程序再写一边， 可是总是由于入职须要学习的东西太多， 没有时间。

程序早就写好了。 最终有机会贴出来了。o(∩∩)o..

最早的时候我採用C实现的效果并不好。 当时也没有认真调试。 最初的时候採用C#实现的效果反而不错， 由于C#有非常多方便的类库能够获取CPU的占用率， 控制sleep时间等等。事实上在C中也非常easy实现。

整体的算法思想， 这里就不再反复了， 能够參考以下的链接 ：

http://blog.csdn.net/watkinsong/article/details/6865775

http://blog.csdn.net/watkinsong/article/details/6867373

http://blog.csdn.net/watkinsong/article/details/6867473

http://blog.csdn.net/watkinsong/article/details/6867666

http://blog.csdn.net/watkinsong/article/details/6870748

http://blog.csdn.net/watkinsong/article/details/6871235

本次算法的实现， 全部的代码都托管到了github, 而且使用了makefile编译文件。

地址： https://github.com/weixsong/aventador

以下简单的给出代码和效果截图。 这里的效果实现比曾经的C#实现的那个sin曲线要好一些。

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sched.h>
#include <unistd.h>

extern const double PI = 3.1415926;

// setup the cpu set of this program to run on
int set_cpu(int id)
{
    cpu_set_t mask;
    CPU_ZERO(&mask);
    CPU_SET(id, &mask);
    if (sched_setaffinity(0, sizeof(mask), &mask) == -1)
    {
        fprintf(stderr, "warning: could not set CPU affinity/n");
        return 0;
    }
    return 1;
}

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

#include "CPUtils.h"

const int CPU_KERNEL_ID = 0x0003;

const int SAMPLE_COUNT = 200;
const int TIME_SLICE = 200; // ms in second
const int TIME_TRANFORM = 1000; // change ms to us
long * busy_span;

// init the busy span, this is used to control the cpu busy time for each sample point
int init_busySpan(int sample_count)
{
	busy_span = (long *)malloc(sample_count * sizeof(long));
	if(busy_span == NULL)
	{
		return -1;
	}
	double radian = 0.0;
	double radianIncrement = 2.0 / (double)sample_count;
	int amplitude = (int)(TIME_SLICE / 2); // amplitude of sin curves, it means half of the time slice because sin() has negative value

	int i;
	for(i = 0; i < sample_count; i++)
	{
		busy_span[i] = (long)(amplitude + sin(radian * PI) * amplitude);
		radian = radian + radianIncrement;
	}
	return 1;
}

int main(void)
{
	if(set_cpu(CPU_KERNEL_ID) == 0)
	{
		printf("cpu affinity set failed\n");
	}
	else
	{
		printf("cpu affinity set succeeded\n");
	}

	printf("clock per second:%ld \n", CLOCKS_PER_SEC);
	fflush(stdout);

	if(!(init_busySpan(SAMPLE_COUNT)))
	{
		printf("init error \n");
		return 0;
	}

	int i = 0;
	long busy_time; // us
	long sleep_time; // us
	clock_t begin;
	for(i = 0; ; i = (i + 1) % SAMPLE_COUNT)
	{
		busy_time = busy_span[i] * TIME_TRANFORM;
		begin = clock();
		while((clock() - begin) < busy_time)
		{
			// loop
		}
		sleep_time = (long)((TIME_SLICE - busy_span[i])) * TIME_TRANFORM;
		usleep(sleep_time);
	}

	return 1;
}