Re: [Qemu-devel] [virtio-dev] Re: [virtio-dev] Re: [PATCH v2 00/16] Vhost-pci for inter-VM communication

[Jason Wang <jasowang@redhat.com>]

On 2017年05月23日 18:48, Wei Wang wrote:
> On 05/23/2017 02:32 PM, Jason Wang wrote:
> > On 2017年05月23日 13:47, Wei Wang wrote:
> > > On 05/23/2017 10:08 AM, Jason Wang wrote:
> > > > On 2017年05月22日 19:46, Wang, Wei W wrote:
> > > > > On Monday, May 22, 2017 10:28 AM, Jason Wang wrote:
> > > > > > On 2017年05月19日 23:33, Stefan Hajnoczi wrote:
> > > > > > > On Fri, May 19, 2017 at 11:10:33AM +0800, Jason Wang wrote:
> > > > > > > > On 2017年05月18日 11:03, Wei Wang wrote:
> > > > > > > > > On 05/17/2017 02:22 PM, Jason Wang wrote:
> > > > > > > > > > On 2017年05月17日 14:16, Jason Wang wrote:
> > > > > > > > > > > On 2017年05月16日 15:12, Wei Wang wrote:
> > > > > > > > > > > > > Hi:
> > > > > > > > > > > > >
> > > > > > > > > > > > > Care to post the driver codes too?
> > > > > > > > > > > > OK. It may take some time to clean up the driver code 
> > > > > > > > > > > > before post
> > > > > > > > > > > > it out. You can first have a check of the draft at the repo 
> > > > > > > > > > > > here:
> > > > > > > > > > > > https://github.com/wei-w-wang/vhost-pci-driver
> > > > > > > > > > > >
> > > > > > > > > > > > Best,
> > > > > > > > > > > > Wei
> > > > > > > > > > > Interesting, looks like there's one copy on tx side. We used to
> > > > > > > > > > > have zerocopy support for tun for VM2VM traffic. Could you 
> > > > > > > > > > > please
> > > > > > > > > > > try to compare it with your vhost-pci-net by:
> > > > > > > > > We can analyze from the whole data path - from VM1's network 
> > > > > > > > > stack
> > > > > > > > > to send packets -> VM2's network stack to receive packets. The
> > > > > > > > > number of copies are actually the same for both.
> > > > > > > > That's why I'm asking you to compare the performance. The only 
> > > > > > > > reason
> > > > > > > > for vhost-pci is performance. You should prove it.
> > > > > > > There is another reason for vhost-pci besides maximum performance:
> > > > > > >
> > > > > > > vhost-pci makes it possible for end-users to run networking or 
> > > > > > > storage
> > > > > > > appliances in compute clouds.  Cloud providers do not allow 
> > > > > > > end-users
> > > > > > > to run custom vhost-user processes on the host so you need 
> > > > > > > vhost-pci.
> > > > > > >
> > > > > > > Stefan
> > > > > > Then it has non NFV use cases and the question goes back to the 
> > > > > > performance
> > > > > > comparing between vhost-pci and zerocopy vhost_net. If it does 
> > > > > > not perform
> > > > > > better, it was less interesting at least in this case.
> > > > > Probably I can share what we got about vhost-pci and vhost-user:
> > > > > https://github.com/wei-w-wang/vhost-pci-discussion/blob/master/vhost_pci_vs_vhost_user.pdf 
> > > > >
> > > > > Right now, I don’t have the environment to add the vhost_net test.
> > > >
> > > > Thanks, the number looks good. But I have some questions:
> > > >
> > > > - Is the number measured through your vhost-pci kernel driver code?
> > >
> > > Yes, the kernel driver code.
> >
> > Interesting, in the above link, "l2fwd" was used in vhost-pci 
> > testing. I want to know more about the test configuration: If l2fwd 
> > is the one that dpdk had, want to know how can you make it work for 
> > kernel driver. (Maybe packet socket I think?) If not, want to know 
> > how do you configure it (e.g through bridge or act_mirred or others). 
> > And in OVS dpdk, is dpdk l2fwd + pmd used in the testing?
>
> Oh, that l2fwd is a kernel module from OPNFV vsperf
> (http://artifacts.opnfv.org/vswitchperf/docs/userguide/quickstart.html)
> For both legacy and vhost-pci cases, they use the same l2fwd module.
> No bridge is used, the module already works at L2 to forward packets
> between two net devices.

Thanks for the pointer. Just to confirm, I think virtio-net kernel 
driver is used in OVS-dpdk test?

Another question is, can we manage to remove the copy in tx? If not, is 
it a limitation of virtio protocol?

Thanks

> Best,
> Wei