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！

复制代码 代码如下:
#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:%ld\n", end - start);

for(i = 0; i < MAX_LEN； i++)
array[i]++;

prefetchnta(array);
start = GetCPUTickCount();
array[0]++;
end = GetCPUTickCount();
printf("use prefetch time:%ld\n", end - start);

return 0;
}