Re: Question about memcpy

July 8, 2018

      void *p = malloc(4096 * max);
start = usec();
for (i = 0; i < max; i++) {
memcpy(p + i * 4096, page, 4096);
}
end = usec();
printf("%s : %d time use %lu us \n", __func__, max,end - start）;

static unsigned long usec(void)
{
        struct timeval tv;
        gettimeofday(&tv, 0);
        return (unsigned long)tv.tv_sec * 1000000 + tv.tv_usec;
}

I'm don't think it's really precise but i did notice a difference ,

2018-07-08 2:44 GMT+08:00 <valdis.kletnieks@vt.edu>:
...
On Sat, 07 Jul 2018 19:36:47 +0800, bing zhu said:
...
and in user space i do the same thing,I noticed that kernel is faster
than
user ,
How did you measure the times? Doing this right is actually harder than it
looks...