[dpdk-dev] [PATCH v2 0/5] Optimize memcpy for AVX512 platforms

[Wang, Zhihong]

> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Tuesday, January 19, 2016 4:06 AM
> To: Wang, Zhihong <zhihong.wang at intel.com>
> Cc: dev at dpdk.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>;
> Richardson, Bruce <bruce.richardson at intel.com>; Xie, Huawei
> <huawei.xie at intel.com>
> Subject: Re: [PATCH v2 0/5] Optimize memcpy for AVX512 platforms
> 
> On Sun, 17 Jan 2016 22:05:09 -0500
> Zhihong Wang <zhihong.wang at intel.com> wrote:
> 
> > This patch set optimizes DPDK memcpy for AVX512 platforms, to make full
> > utilization of hardware resources and deliver high performance.
> >
> > In current DPDK, memcpy holds a large proportion of execution time in
> > libs like Vhost, especially for large packets, and this patch can bring
> > considerable benefits.
> >
> > The implementation is based on the current DPDK memcpy framework, some
> > background introduction can be found in these threads:
> > http://dpdk.org/ml/archives/dev/2014-November/008158.html
> > http://dpdk.org/ml/archives/dev/2015-January/011800.html
> >
> > Code changes are:
> >
> >   1. Read CPUID to check if AVX512 is supported by CPU
> >
> >   2. Predefine AVX512 macro if AVX512 is enabled by compiler
> >
> >   3. Implement AVX512 memcpy and choose the right implementation based
> on
> >      predefined macros
> >
> >   4. Decide alignment unit for memcpy perf test based on predefined macros
> 
> Cool, I like it. How much impact does this have on VHOST?

The impact is significant especially for enqueue (Detailed numbers might not
be appropriate here due to policy :-), only how I test it), because VHOST actually
spends a lot of time doing memcpy. Simply measure 1024B RX/TX time cost and
compare it with 64B's and you'll get a sense of it, although not precise.

My test cases include NIC2VM2NIC and VM2VM scenarios, which are the main
use cases currently, and use both throughput and RX/TX cycles for evaluation.