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.

Thanks