Hi, Thomas
> -----Original Message-----
> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Thursday, November 2, 2017 6:45 PM
> To: Wang, Zhihong <zhihong.w...@intel.com>; Li, Xiaoyun
> <xiaoyun...@intel.com>
> Cc: dev@dpdk.org; Richardson, Bruce <bruce.richard...@intel.com>;
> Ananyev, Konstantin <konstantin.anan...@intel.com>; Lu, Wenzhuo
> <wenzhuo...@intel.com>; Zhang, Helin <helin.zh...@intel.com>;
> ophi...@mellanox.com
> Subject: Re: [dpdk-dev] [PATCH v8 1/3] eal/x86: run-time dispatch over
> memcpy
>
> 02/11/2017 11:22, Wang, Zhihong:
> > > I don't know what is creating this drop exactly.
> > > When doing different tests on different environments, we do not see
> this
> > > drop.
> > > If nobody else can see such issue, I guess we can ignore it.
> >
> > Hi Thomas, Xiaoyun,
> >
> > With this patch (commit 84cc318424d49372dd2a5fbf3cf84426bf95acce) I see
> > more than 20% performance drop in vhost loopback test with testpmd
> > macswap for 256 bytes packets, which means it impacts actual vSwitching
> > performance.
> >
> > Suggest we fix it or revert it for this release.
>
> I think we need more numbers to take a decision.
> What is the benefit of this patch? In which use-cases?
> What are the drawbacks? In which use-cases?
>
> Please, it is a call to test performance with and without this patch
> in more environments (CPU, packet size, applications).
Following is the performance drop we observe in vhost/virtio loopback
performance
with and without this patch
Test application: testpmd
CPU info: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz
OS: Ubuntu 16.04
Mergebale Path
packet size Performance Drop
64 -1.30%
128 0.81%
158 -19.17%
188 -19.18%
218 -16.29%
230 -16.57%
256 -16.77%
280 -3.07%
300 -3.22%
380 -2.44%
420 -1.65%
512 -0.99%
1024 0.00%
1518 -0.68%
Vector Path
packet size Performance Drop
64 3.30%
128 7.18%
256 -12.77%
512 -0.98%
1024 0.27%
1518 0.68%
