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

Tetsuya.Mukawa mukawa at igel.co.jp
Wed Aug 27 07:27:42 CEST 2014

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.


> Regards,
> Changchun
>> -----Original Message-----
>> From: Tetsuya.Mukawa [mailto:mukawa at igel.co.jp]
>> Sent: Wednesday, August 27, 2014 12:39 PM
>> To: Ouyang, Changchun; dev at dpdk.org
>> Cc: Xie, Huawei; Katsuya MATSUBARA; nakajima.yoshihiro at lab.ntt.co.jp;
>> 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 at dpdk.org] On Behalf Of Xie, Huawei
>>> Sent: Tuesday, August 26, 2014 7:06 PM
>>> To: dev at dpdk.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

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