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

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, February 7, 2023 10:09 AM
> 
> On Tue, Feb 07, 2023 at 04:56:06PM +0200, Alvaro Karsz wrote:
> > > An example of a question is this: we have two RX queues say 1 and 2
> > > each with a distinct interrupt vector. coalescing is set to 10
> > > packets.  Now
> > > 9 packets arrive on queue 1 and 1 on queue 2. Do you expect an
> > > interrupt? If yes which one - 1 or 2 or both?
> >
> > Sorry, I wasn't clear enough.
> > In this case, you should not issue an interrupt until one of the
> > queues receives the 10'th packet.
> > The counters are per queue, the coalescing parameters (usecs and
> > max_packets) are global.
> >
Counters and parameters go hand-in hand.
It should be per VQ.

> > I agree that this should be mentioned in the spec, I missed it.
> 
> Right. So in my humble opinion, ability to configure parameters per queue is
> not completely free, as this is doubling the memory requirements.
> Sounds like a feature bit is somewhat justified. No?
> 
> --
> MST