Re: [Minios-devel] [PATCH v3 20/43] mini-os: implement the memmove/memchr

[Huang Shijie <shijie.huang@xxxxxxx>]

On Thu, Apr 26, 2018 at 10:03:58AM +0100, Julien Grall wrote:
> 
> 
> On 26/04/18 09:59, Huang Shijie wrote:
> >On Thu, Apr 26, 2018 at 09:49:20AM +0100, Julien Grall wrote:
> >>
> >>
> >>On 26/04/18 09:42, Huang Shijie wrote:
> >>>On Wed, Apr 25, 2018 at 11:09:43AM +0100, Julien Grall wrote:
> >>>>
> >>>>
> >>>>On 25/04/18 10:37, Huang Shijie wrote:
> >>>>>On Wed, Apr 25, 2018 at 10:10:58AM +0100, Julien Grall wrote:
> >>>>>>
> >>>>>>
> >>>>>>On 04/16/2018 07:32 AM, Huang Shijie wrote:
> >>>>>>>This patch is split from the Chen Baozi's old patch:
> >>>>>>>
> >>>>>>>"This activates the ARM code added in the previous patches. On
> >>>>>>>  ARM, Mini-OS will boot and display some output on the console. 
> >>>>>>> Tested with:"
> >>>>>>>
> >>>>>>>Note: The code is copied from FreeBSD code:
> >>>>>>>       freebsd/contrib/ldns/compat/memmove.c
> >>>>>>
> >>>>>>That's only for memmove. How about memchr?
> >>>>>The memchr is also from the FreeBSD code...
> >>>>
> >>>>You specify the file for memmove.c. But not memchr.
> >>>>
> >>>>Also, this seems to come from a userspace application and not the kernel.
> >>>>Why not importing the assembly version (memmove.S and memcpy.S) that has
> >>>>been optimized for aarch64?
> >>>okay. I can use the assembly version..
> >>
> >>I was asking the rationale behind using userspace application memcpy over
> >>the assembly one.
> >I did not check the rationale behind.
> >It works, then I used it.
> >
> >I prefer to the C version which maybe used by x86. The assembly version is 
> >only
> >for arm64...
> 
> Well if there are an assembly version, then most likely there are a reason
> behind :).
The assembly version is for better performance. :)

> 
> If you look around most of the time there will be a generic version
> implemented in C and each architecture can override it for there own
> version. This is how it is done in glibc, Linux, Xen, FreeBSD...
Yes, I know that.

> 
> Anyway, that's not overly critical it seems to be only used at boot time.
Yes, it is not critical. So, let's keep the C version :)

Thanks
Huang Shijie

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