netdev - Re: [RFC] Discuss about an new idea "Vsock over Virtio-net"

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Date:   Thu, 15 Nov 2018 03:10:13 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     jiangyiwen <jiangyiwen@...wei.com>
Cc:     stefanha@...hat.com, stefanha@...il.com,
        Jason Wang <jasowang@...hat.com>, netdev@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [RFC] Discuss about an new idea "Vsock over Virtio-net"

On Thu, Nov 15, 2018 at 03:38:15PM +0800, jiangyiwen wrote:
> On 2018/11/15 15:04, Michael S. Tsirkin wrote:
> > On Thu, Nov 15, 2018 at 11:56:03AM +0800, jiangyiwen wrote:
> >> Hi Stefan, Michael, Jason and everyone,
> >>
> >> Several days ago, I discussed with jason about "Vsock over Virtio-net".
> >> This idea has two advantages:
> >> First, it can use many great features of virtio-net, like batching,
> >> mergeable rx buffer and multiqueue, etc.
> >> Second, it can reduce many duplicate codes and make it easy to be
> >> maintained.
> > 
> > I'm not sure I get the motivation. Which features of
> > virtio net are relevant to vsock? The ones that you mention
> > all seem to be mostly of use to the networking stack.
> > 
> > 
> >> Before the implement, I want to discuss with everyone again, and
> >> want to know everyone's suggestions.
> >>
> >> After the discussion, based on this point I will try to implement
> >> this idea, but I am not familiar with the virtio-net, that is a
> >> pity. :(
> >>
> >> -------------------------Simple idea------------------------------
> >>
> >> 1. The packet layout will become as follows:
> >>
> >> +---------------------------------+
> >> |        Virtio-net header        |
> >> |(struct virtio_net_hdr_mrg_rxbuf)|
> > 
> > Which fields in virtio_net_hdr_mrg_rxbuf are of interest to vsock?
> > 
> 
> Hi Michael,
> 
> Yes, currently vsock has poor performance, first, it only support transport
> small packet, in order to make the balance between performance and guest memory.
> 
> In order to solve this problem, there are two features vsock can used,
> mergeable rx buffer and multiqueue. Based on this, there are some shared
> codes vsock can use.
> 
> Thanks,
> Yiwen.

Supporting more queues with vsock is probably significantly
less work than a completely new interface.
For mergeable, as buffers are split arbitrarily, why can't you combine
them within guest driver before sending them up the stack?
Probably better than relying on host to do it.

> >> +---------------------------------+
> >> |          Vsock header           |
> >> |    (struct virtio_vsock_hdr)    |
> >> +---------------------------------+
> >> |             payload             |
> >> |      (until end of packet)      |
> >> +---------------------------------+
> > 
> > Thanks,
> > 
>