[dpdk-dev] [PATCH 1/3] eal/x86: run-time dispatch over memcpy

[Lu, Wenzhuo]

Hi Stephen,


> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Thursday, August 31, 2017 2:01 AM
> To: Li, Xiaoyun <xiaoyun.li at intel.com>
> Cc: Richardson, Bruce <bruce.richardson at intel.com>; dev at dpdk.org; Lu,
> Wenzhuo <wenzhuo.lu at intel.com>; Wang, Zhihong
> <zhihong.wang at intel.com>; Zhang, Qi Z <qi.z.zhang at intel.com>
> Subject: Re: [dpdk-dev] [PATCH 1/3] eal/x86: run-time dispatch over memcpy
> 
> On Fri, 25 Aug 2017 10:06:11 +0800
> Xiaoyun Li <xiaoyun.li at intel.com> wrote:
> 
> > This patch dynamically selects functions of memcpy at run-time based
> > on CPU flags that current machine supports. This patch uses function
> > pointers which are bind to the relative functions at constrctor time.
> > To make AVX512 instructions pass compilation, enable the switch in
> > makefile.
> >
> > Signed-off-by: Xiaoyun Li <xiaoyun.li at intel.com>
> 
> Recent versions of GCC also have better ways to handle this.
I think the assumption of using the instructions is that we believe we can do better than the compiler. If it turns out not, maybe we need to change the instructions back to C. But it's another story.