Re: [dpdk-dev] [RFC][PATCH V2 1/3] examples/vhost: Add vswitch (generic switch) framework

[Pankaj Chauhan <pankaj.chauhan@nxp.com>]

On 9/19/2016 8:13 PM, Yuanhan Liu wrote:
> Firstly, sorry for being late on this discussion: I just got a chance
> to follow what you guys were talking about.
>
> On Tue, Sep 13, 2016 at 02:51:31PM +0800, Tan, Jianfeng wrote:
>>> (2) we'd better not differentiate phys device and virtual
>
> Agreed.
>
>>>> device in generic framework (it's just an attribute of vswitch_port.
>>>>
>>>> What do you think?
>>>
>>> I agree with your thought that given the current API in this patchset we
>>> should aim for making switch_worker agnostic of the port type. Ideally it
>>> should look something like this:
>>>
>>> switch_worker() {
>>>
>>>        rx_port mask = VSWITCH_PTYPE_PHYS | VSWITCH_PTYPE_PHYS;
>>>
>>>        rx_port = vs_sched_rx_port(vswit_dev_g, rx_port_mask, core_id)
>>>        rx_q = rx_port->get_rxq(vs_port, vdev, code_id);
>>>        rx_port->do_rx(rx_port, rxq, NULL, pktss, MAX_PKT_BURST);
>>
>> Can we hide queues inside struct vswitch_port? I mean:
>> For VMDQ switch, treat (port_id, queue_id) as a vswitch_port, so far you've
>> already stored "struct vhost_dev *" into vswitch_port.priv when it's a
>> virtual port, how about store queue_id into vswitch_port.priv when it's a
>> physical port.
>
> Well, note that vhost-user also supports multiple queue; it's just
> haven't been enabled yet. So, storing "vdev" for virtio port and
> "queue_id" for phys port doesn't make too much sense.
>
>> For arp_learning switch, make (port_id, all_enabled_queues) as a
>> vswitch_port.
>> Summarize above two: we treat (port_id, all_enabled_queues[]) as a
>> vswitch_port.
>>
>> How about it?
>
> Sorry, I don't quite like the idea. It's weird to use "vswitch_port + queue_id"
> combination to represent a port. A vswitch_port should be just a port: let's
> keep the logic that simple.
>

We wanted to take that approach to make vhost/main.c agnostic port type 
and have common code for rx/tx processing. The current version of 
patchset (v2) takes care of multiqueue, as it calls 
vs_port->get_txq/get_rxq to get the queue on which rx/tx has to be 
performed. This way the underlying switch can decide the queue based on 
core_id and vs_port.

But in the v2 patchset we still bind vhost_dev to the cores, and pass it 
to vs_port->get_rxq() to get the rx_queue corresponding to vhost_dev. 
Jianfeng had suggested to remove vhost_dev to core binding, and bind 
vs_port to the cores. Creating one vswitch_port for a physical port + 
queue_id was a step in that direction, thus creating very generic code 
in vhost/main.c.

YLiu/Jianfeng,

Please suggest what approach we should take here? Should we keep the 
logic of binding vhost_dev to core (as in V2 patchset), thus leaving 
some intelligence about vhost_dev in vhost/main.c.

Or What other options do you suggest if we want to achieve port type 
agnostic vhost/main.c

Thanks,
Pankaj