cpu时钟预取实例代码分享

#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;
}