[virtio-dev] Re: [virtio-comment] Re: About custom device counter

Michael S. Tsirkin
2023-06-19T14:21:03Z

On Mon, Jun 19, 2023 at 12:33:33PM +0000, Parav Pandit wrote:
>
>
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Friday, June 16, 2023 10:13 AM
> > > Such as "limit", in a cloud scenario, multiple users purchase
> > > different VMs, and these VMs share the capabilities of the same host.
> > > In order to ensure that each VM will not affect others, the network
> > > card(virtio-net) capability of each VM is limited. When these users purchase
> > VMs, this limit has already been determined.
> > > So if the network card traffic of a vm exceeds the upper limit, packet
> > > loss will occur. It is necessary for us to count these packet losses.
> > > And the device should expose to the user.
> >
> > OK so here, driver is expected to rate limit yes?
> >
> Some implementations of txq are lossy and some are not creating backpressure/flow control to driver so driver can rate limit it naturally.
> So a tx packet drop counter is needed to cover the lossy implementations which is abstract enough regardless of reason on why device dropped it.

Yes but Xuan Zhuo here is saying that he wants a register that is
like link speed, not a counter.

> A more granular counter becomes vendor specific that we can possibly avoid or place under different command.

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MST