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 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?

>
>> - Have you tested packet size other than 64B?
>
> Not yet.

Better to test more since the time spent on 64B copy should be very fast.

>
>> - Is zerocopy supported in OVS-dpdk? If yes, is it enabled in your test?
> zerocopy is not used in the test, but I don't think zerocopy can increase
> the throughput to 2x.

I agree, but we need prove this with numbers.

Thanks

> On the other side, we haven't put effort to optimize
> the draft kernel driver yet.
>
> Best,
> Wei
>