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Subject: Re: [virtio-dev] Re: [virtio-comment] [PATCH v3] virtio-net: support the virtqueue coalescing moderation


> > Maybe we can use struct virtio_net_ctrl_coal inside struct
> > virtio_net_ctrl_coal_vq instead of repeating max_usecs and
> > max_packets?
> > I'm not sure if it would be confusing, what do you think?
> >
>
> Hi Alvaro.
>
> I guess you mean one of the following two forms:
>
> #1
> struct virtio_net_ctrl_coal {
>     le32 max_packets;
>     le32 max_usecs;
> };
>
> struct virtio_net_ctrl_coal_vq {
>     le16 vqn;
>     le16 reserved;
>     struct virtio_net_ctrl_coal coal;
> } coal_vq;
>
> #2
> struct virtio_net_ctrl_coal {
>     le32 max_packets;
>     le32 max_usecs;
>     le16 vqn; // if _F_VQ_NOTF_COAL is negotiated
>     le16 reserved; // if _F_VQ_NOTF_COAL is negotiated
> };
>
> If it's #1, I think the format is a bit ugly, it's not semantic to use coal_vq to send global commands when _F_VQ_NOTF_COAL is not negotiated, and the presence of vqn and reserved is awkward.
> If it's #2, I think this is a bit like the v1 version, using virtio_net_ctrl_coal as a virtual queue to send commands does not seem to be semantic, but it is indeed more unified in function.
>
> I think we should hear from Michael and Parav.
>

I meant #1.
We can see virtio_net_ctrl_coal as a struct holding coalescing
parameters, regardless of the commands.
Yes, let's wait for more comments on that.

> > > +Virtqueue coalescing parameters:
> > > +\begin{itemize}
> > > +\item \field{vqn}: The virtqueue number of the enabled transmit or receive virtqueue, excluding the control virtqueue.
> > > +\item \field{max_packets}: The maximum number of packets sent/received by the specified virtqueue before a TX/RX notification.
> > > +\item \field{max_usecs}: The maximum number of TX/RX usecs that the specified virtqueue delays a TX/RX notification.
> > > +\end{itemize}
> > > +
> > > +\field{reserved} is reserved and it is ignored by the device.
> > > +
> >
> > max_packets is the same with VIRTIO_NET_CTRL_NOTF_COAL_VQ_SET and with
> > VIRTIO_NET_CTRL_NOTF_COAL_[T/R]X_SET.
> > ("Maximum number of packets to receive/send before a RX/TX notification").
> > The fact that this is applied to all VQs or to a specific one is
> > derived from the command.
> > Same for max_usecs.
> > Maybe we can join the coalescing parameters somehow instead of
> > repeating the explanations?
> >

Any thoughts on this part?


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