Re: [RFC] lib/librte_vhost: qemu vhost-user support into DPDK vhost library

["Tetsuya.Mukawa" <mukawa-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org>]

Hi Changchun,

(2014/08/27 14:01), Ouyang, Changchun wrote:
> Agree with you, the performance should be same as the data path (RX/TX) is not affected,
> The difference between implementation only exists in the virtio device creation and destroy stage.
Yes, I agree. Also There may be the difference, if a virtio-net driver
on a guest isn't poll mode like a virtio-net device driver in the
kernel. In the case, existing vhost implementation uses the eventfd
kernel module, and vhost-user implementation uses eventfd to kick the
driver. So I guess there will be the difference.

Anyway, about device creation and destruction, the difference will come
from transmission speed between unix domain socket and CUSE. I am not
sure which is faster.

Thanks,
Tetsuya


>
> Regards,
> Changchun
>
>> -----Original Message-----
>> From: Tetsuya.Mukawa [mailto:mukawa-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org]
>> Sent: Wednesday, August 27, 2014 12:39 PM
>> To: Ouyang, Changchun; dev-VfR2kkLFssw@public.gmane.org
>> Cc: Xie, Huawei; Katsuya MATSUBARA; nakajima.yoshihiro-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org;
>> Hitoshi Masutani
>> Subject: Re: [dpdk-dev] [RFC] lib/librte_vhost: qemu vhost-user support into
>> DPDK vhost library
>>
>>
>> (2014/08/27 9:43), Ouyang, Changchun wrote:
>>> Do we have performance comparison between both implementation?
>> Hi Changchun,
>>
>> If DPDK applications are running on both guest and host side, the
>> performance should be almost same, because while transmitting data virt
>> queues are accessed by virtio-net PMD and libvhost. In libvhost, the existing
>> vhost implementation and a vhost-user implementation will shares or uses
>> same code to access virt queues. So I guess the performance will be almost
>> same.
>>
>> Thanks,
>> Tetsuya
>>
>>
>>> Thanks
>>> Changchun
>>>
>>>
>>> -----Original Message-----
>>> From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of Xie, Huawei
>>> Sent: Tuesday, August 26, 2014 7:06 PM
>>> To: dev-VfR2kkLFssw@public.gmane.org
>>> Subject: Re: [dpdk-dev] [RFC] lib/librte_vhost: qemu vhost-user
>>> support into DPDK vhost library
>>>
>>> Hi all:
>>> We are implementing qemu official vhost-user interface into DPDK vhost
>> library, so there would be two coexisting implementations for user space
>> vhost backend.
>>> Pro and cons in my mind:
>>> Existing solution:
>>> Pros:  works with qemu version before 2.1;  Cons: depends on eventfd
>> proxy kernel module and extra maintenance effort Qemu vhost-user:
>>>                Pros:  qemu official us-vhost interface;     Cons: only available after
>> qemu 2.1
>>> BR.
>>> huawei