Thank you ,I use this func for both kernel and user ,result are same.
void *memcpy(void *dest, const void *src, size_t n)
{
long d0, d1, d2;
asm volatile(
"rep ; movsq\n\t"
"movq %4,%%rcx\n\t"
"rep ; movsb\n\t"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
: "0" (n >> 3), "g" (n & 7), "1" (dest), "2" (src)
: "memory");
return dest;
}
kernel is indeed faster than user.
2018-07-10 14:22 GMT+08:00 Greg KH <greg@xxxxxxxxx>:
On Tue, Jul 10, 2018 at 12:50:21PM +0800, bing zhu wrote:
> I agree !,just i think the problem is still there,memcpy is indeed faster in
> kernel than in user,i've tried both ways .
Make sure you are actually using the same code for memcpy in both
places. Do not rely on your libc or the kernel library for such a
thing, otherwise you are not comparing the same code exactly.
> schedule might be to blame.
Lots of things "might be to blame", but first off, try to work out
exactly what you are trying to test, and why, and work on that.
good luck!
greg k-h
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