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

(2014/08/27 14:27), Tetsuya.Mukawa wrote:

Hi Changchun,

(2014/08/27 14:01), Ouyang, Changchun wrote:

quoted

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.

Thank for pointing out my misleading expression.

Correct: transmission latency
Incorrect: transmission speed

Tetsuya,

Thanks,
Tetsuya

quoted

Regards,
Changchun

quoted

-----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:

quoted

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

quoted

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.

quoted

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:

quoted

               Pros:  qemu official us-vhost interface;     Cons: only available after

qemu 2.1

quoted

BR.
huawei