cpu时钟预取实例代码分享

测试下预取的效果，利用CPU始终查看效果。根据实验发现，预取地址在地址使用之前的十行左右代码处效果比较好！

#include <stdio.h>

#define MAX_LEN 1000000
static inline void prefetchnta(void *addr) //预取部分
{
    __asm__("movl %0, %%eax"::"a"(addr));
    __asm__(".byte 0x0f, 0x18, 0x00");
}
inline unsigned long long GetCPUTickCount()
{
    unsigned long high32 = 0;
    unsigned long low32 = 0;
    __asm__("RDTSC" : "=a"(low32), "=d"(high32));
    unsigned long long counter = high32;
    counter = (counter<<32) + low32;
    return counter;
}
int main(int argc, char* argv[])
{
    long long start, end;
    long long array[MAX_LEN];
    int i;
    for(i = 0; i < MAX_LEN； i++) //让cache失效
        array[i]++;
    start = GetCPUTickCount();
    array[0]++;
    end = GetCPUTickCount();
    printf("don't use prefetch time:%ldn", end - start);

    for(i = 0; i < MAX_LEN； i++)
        array[i]++;
    prefetchnta(array);
    start = GetCPUTickCount();
    array[0]++;
    end = GetCPUTickCount();
    printf("use prefetch time:%ldn", end - start);
    return 0;
}