Re: [Qemu-devel] vhost-pci and virtio-vhost-user

[Wei Wang <wei.w.wang@intel.com>]

On 01/16/2018 01:33 PM, Jason Wang wrote:
>
>
> On 2018年01月15日 18:43, Wei Wang wrote:
>> On 01/15/2018 04:34 PM, Jason Wang wrote:
>>>
>>>
>>> On 2018年01月15日 15:59, Wei Wang wrote:
>>>> On 01/15/2018 02:56 PM, Jason Wang wrote:
>>>>>
>>>>>
>>>>> On 2018年01月12日 18:18, Stefan Hajnoczi wrote:
>>>>>>
>>>>>
>>>>> I just fail understand why we can't do software defined network or 
>>>>> storage with exist virtio device/drivers (or are there any 
>>>>> shortcomings that force us to invent new infrastructure).
>>>>>
>>>>
>>>> Existing virtio-net works with a host central vSwitch, and it has 
>>>> the following disadvantages:
>>>> 1) long code/data path;
>>>> 2) poor scalability; and
>>>> 3) host CPU sacrifice
>>>
>>> Please show me the numbers.
>>
>> Sure. For 64B packet transmission between two VMs: vhost-user reports 
>> ~6.8Mpps, and vhost-pci reports ~11Mpps, which is ~1.62x faster.
>>
>
> This result is kind of incomplete. So still many questions left:
>
> - What's the configuration of the vhost-user?
> - What's the result of e.g 1500 byte?
> - You said it improves scalability, at least I can't get this 
> conclusion just from what you provide here
> - You suspect long code/data path, but no latency numbers to prove it
>

Had an offline meeting with Jason. The future discussion will be more 
focused on the design.

Here is a conclusion about more results we collected for 64B packet 
transmission, compared to ovs-dpdk (though we are comparing to ovs-dpdk 
here, but vhost-pci isn't meant to replace ovs-dpdk. It's for inter-VM 
communication, and packets going to the outside world will go from the 
traditional backend like ovs-dpdk):

1) 2VM communication: over 1.6x higher throughput;
2) 22% shorter latency;
3) in the 5-VM chain communication tests, vhost-pci shows ~6.5x higher 
throughput thanks to its better scalability

We'll provide 1500B test results later.

Best,
Wei