Windows控制CPU使用率曲线

    前几天无聊，按照《编程之美》第一题写了个控制CPU使用率的程序。本以为没什么，可是今天早上在ChinaUnix上看到完全复制书上的代码毫无原创的帖子居然很火。。。所以把自己的代码贴出来，供以后学习……

    效果图如下：

 

    其实程序的设计思想很简单，Windows任务管理器中CPU使用率基本上1s刷新一次，而CPU使用率其实就是在1s中CPU忙和闲时间的均值。因此，根据我们想要得到的CPU曲线的特点，我们首先做出忙闲时间的表，CPU根据忙闲时间选择执行或挂起。

代码如下：

 #include <windows.h>#include <stdlib.h>#include <math.h>#define COUNT200const doubleSPLIT = 0.01;const doublePI = 3.14159265;const doubleSLOPE = 150;const int INTERVAL = 300;DWORD WINAPI SineThread(LPVOID Sine){DWORD busySpan[COUNT];DWORD idleSpan[COUNT];int half = INTERVAL/2;double radian = 0.0;DWORD startTime;int i;for (i=0; i<COUNT; i++){busySpan[i] = (DWORD)(half + half*sin(PI*radian));idleSpan[i] = (DWORD)(INTERVAL - busySpan[i]);radian += SPLIT;}i = 0;while(1){i %= COUNT;startTime = GetTickCount();while((GetTickCount()-startTime) <= busySpan[i]);Sleep(idleSpan[i]);i++;}return 0;}DWORD WINAPI SawThread(LPVOID Saw){DWORD busySpan[COUNT];DWORD idleSpan[COUNT];int half = INTERVAL/2;double radian = 0.0;DWORD startTime;int i;for (i=0; i<COUNT; i++){busySpan[i] = (DWORD)(SLOPE*radian);idleSpan[i] = (DWORD)(INTERVAL - busySpan[i]);radian += SPLIT;}i = 0;while(1){i %= COUNT;startTime = GetTickCount();while((GetTickCount()-startTime) <= busySpan[i]);Sleep(idleSpan[i]);i++;}return 0;}int main(){HANDLE hThread1, hThread2;DWORD dwThreadId1, dwThreadId2;hThread1 = CreateThread(NULL, 0, SineThread, 0, CREATE_SUSPENDED, &dwThreadId1);hThread2 = CreateThread(NULL, 0, SawThread, 0, CREATE_SUSPENDED, &dwThreadId2);SetThreadAffinityMask(hThread1, 1);SetThreadAffinityMask(hThread2, 2);ResumeThread(hThread1);ResumeThread(hThread2);SuspendThread(GetCurrentThread());return 0;}

    其中INTERVAL可以视为周期，而COUNT和SPLIT分别为采样点数和步长，SLOPE就是斜率了。。。另外，对于双核而言，编程之美上的代码并不完美，于是按照书上的指点，使用SetThreadAffinityMask()将两个线程分别在每个核去执行。

Linux下代码完全仿照Windows写出，知识获取时间的函数不同，另外，使用usleep实现微秒级定时：
#include <unistd.h>#include <stdlib.h>#include <math.h>#include <time.h>#include <sys/time.h>#define COUNT200#define SPLIT0.01#define PI3.14159265#define INTERVAL100double get_time(){struct timeval tv;gettimeofday(&tv, NULL);return (tv.tv_sec*1000+tv.tv_usec*1.0/1000);/*ms*/}int main(){double busy_span[COUNT];/* need to modify*/double idle_span[COUNT];int half = INTERVAL/2;double radian = 0.0;double start_time;int i;for(i=0; i<COUNT; i++){busy_span[i] = (double)(half + half*sin(PI*radian));idle_span[i] = (double)(INTERVAL - busy_span[i]);radian += SPLIT;}i = 0;while(1){i %= COUNT;start_time = get_time();while((get_time()-start_time) <= busy_span[i]);usleep(idle_span[i]*1000);i++;}return 0;}