Re: [dpdk-dev] [RFC PATCH 0/2] Virtio-net PMD Extension to work on host.

[Tetsuya Mukawa <mukawa@igel.co.jp>]

On 2015/11/20 11:00, Xie, Huawei wrote:
> On 11/20/2015 2:16 AM, Rich Lane wrote:
>> What's the reason for using qemu as a middleman? Couldn't the new PMD
>> itself open /dev/vhost-net or the vhost-user socket and send the commands
>> to set up virtqueues? That was the approach taken by Jianfeng's earlier RFC.
> Rich:
> Our initial POC also has a device simulation layer, but it is linked
> with the DPDK driver as a library.
> As i created that device simulation based on lkvm, and it takes too much
> effort to rewrite it from scratch, so we decide to release a simple
> version without device simulation first.
> Without device simulation, The PMD is pretty simple, standalone, no
> dependency to qtest process.
> With device simulation, we could easily implement other virtio device in
> DPDK easily, like virtio-crypt.

Hi Rich and Xie,

Probably, how to prepare virtio-net device is the difference between
Jianfeng's RFC and our RFC.
The reason why I choose this approach is below.

1. Ease of maintenance
If we have our virtio-net device, we need to spend time to maintain it.
And QEMU virtio-net code is more tested by more virtio-net drivers and
more users. As a result, it should have less bugs.
Also, If we uses QEMU virtio-net code, we only need to maintain QTest
related implementation.
Anyway, QTest is very stable.
Probably we have bugs first, but later, we don't need to maintain it so
much.

2. Extendability
The virtio-net and vhost specification will be extended in the future.
If we have own implementation, we need to maintain more codes.


> Maybe anyway we provide the simple implementation option, for customers
> who don't like the extra complexity to launch a secondary process in
> their container.
> [...]
>
>

For example, for the user who is OK to invoke 2 processes in same
container, just prepare shell script that invokes QTest process and
vhost-user backend process will be enough.

For the users who doesn't want to invoke 2 processes in one container,
anyway they use some kind of orchestration tool, so invoking one more
process/container is not difficult.

I guess the invoking and connecting multiple processes over containers
may not be something special for container users.
(like deploying load balancer, web server and DB)

Tetsuya