in kernel you should use this func:
static unsigned long usec(void)
{
struct timeval tv;
do_gettimeofday(&tv);
return (unsigned long)tv.tv_sec * 1000000 + tv.tv_usec;
}
2018-07-09 15:54 GMT+08:00 袁建鹏 <yuanjp@xxxxxxxxxxx>:
can you show all code kernel and userspace ?Kernel compile options are optimized, very different from userspace.
you can use the same object (memcpy.o) to link userspace program and kernel module.
-----原始邮件-----
发件人:"bing zhu" <zhubohong12@xxxxxxxxx>
发送时间:2018-07-08 22:03:48 (星期日)
收件人: "Valdis Kletnieks" <valdis.kletnieks@xxxxxx>
抄送: kernelnewbies@kernelnewbies.org
主题: Re: Question about memcpy
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@xxxxxx>:
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...
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