RE: [virtio-comment] [PATCH] virtio-net: support per-queue coalescing moderation

[Parav Pandit <parav@nvidia.com>]

> From: Alvaro Karsz <alvaro.karsz@solid-run.com>
> Sent: Wednesday, February 8, 2023 4:56 PM

> > Alvaro,
> > Do you know if any software used it? Can you get some real data?
> 
> I implemented this feature in our DPU, so at least 1 vendor is using this feature

But which software (virtio net driver) in which OS is using this?

> (I will add support for the per vq command of course).
> I really don't know about other vendors..
>
> You are suggesting to reserve the command and feature bit for safety, so, if we
> reserve them, why not just use them? What do we lose here?
> 
If it is used by some unknown software, only that sw breaks by using non release spec.
If we use it by changing the definition, it may break that unknown sw.
If we know there is no known sw, we are better of with redefinition (by adding vqn, and by removing tx,rx from it).

> Not having this feature/command even complicates things now that we are
> talking about removing the RX and TX from the per vq command, how do you
> change parameters to all TX queues? to all RX queues? we'll need 2 special
> indexes, so we now need le32 to hold the queue index.
No need for special index.
How does a driver disable all queues or reset all queues? -> One by one.
So if user want to change for all TXQ, sw can do it one by one by iterating TXQ vqns.