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:%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;

}