一个比较精确计算cpu主频的程序

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <math.h>
#include <windows.h>

static ULONGLONG g_pf_s,g_pf_e,g_sys_freq = {0};
static ULONGLONG g_cycle_s,g_cycle_passed;

//使CPU进入最高性能状态
WINAPI DWORD busy(PVOID param){for(;;);}

inline ULONGLONG rdtsc(void)
{
ULONG hi,lo;
__asm__ __volatile__("rdtsc;movl %%edx,%0;movl %%eax,%1":"=m"(hi),"=m"(lo));
return (ULONGLONG)hi<<32 | lo;
}

void get_sys_freq(void)
{
QueryPerformanceFrequency((PLARGE_INTEGER)&g_sys_freq);
}

static void start(void)
{
QueryPerformanceCounter((PLARGE_INTEGER)&g_pf_s);
g_cycle_s = rdtsc();
}

static void end(void)
{
g_cycle_passed = rdtsc() - g_cycle_s;
QueryPerformanceCounter((PLARGE_INTEGER)&g_pf_e);
}

static void sh_cpu_pf(ULONG *pmhz,double *pmhz_dbl)
{
//实计算际经历的时间
ULONGLONG act_time_passed = (g_pf_e - g_pf_s) * 1000 / g_sys_freq;
ULONG mhz = g_cycle_passed/act_time_passed/1000;
double mhz_dbl = (double)g_cycle_passed/act_time_passed/1000;
printf("sleep act time is %f ms,CPU is %f(%u) MHz\n",(double)act_time_passed,\
mhz_dbl,(unsigned)mhz);
*pmhz=mhz;*pmhz_dbl=mhz_dbl;
}

typedef struct _pf_item
{
ULONG mhz;
double mhz_dbl;
}pf_item,*ppf_item;

int main(int argc,char *argv[])
{
pf_item pf_ary[32];
//将本线程优先级提升到最高以增加测量精度
SetThreadPriority(GetCurrentThread(),THREAD_PRIORITY_HIGHEST);
get_sys_freq();

DWORD tid;
CreateThread(NULL,0,busy,0,0,&tid);
Sleep(1000);

ULONGLONG mhz_total = 0;
double mhz_dbl_total = 0.0f;
for(int i = 0;i<32;i++)
{
start();
Sleep(500);
end();
sh_cpu_pf(&pf_ary[i].mhz,&pf_ary[i].mhz_dbl);
mhz_total += pf_ary[i].mhz;
mhz_dbl_total += pf_ary[i].mhz_dbl;
}
printf("\nLast mhz : %f(%u)\n",mhz_dbl_total/32,(ULONGLONG)floor(mhz_dbl_total/32+0.5));
return 0;
}