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

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Tue, 7 Feb 2023 10:28:37 -0500, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Tue, Feb 07, 2023 at 03:25:55PM +0000, Parav Pandit wrote:
> >
> >
> > > 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.
>
> Well you could have a global parameter and per queue counter.

The global parameter configuration I understand is to configure the counter
of all queues to the same value through a command.

Thanks.


> In fact ethtool only has a global parameter support - how
> will users configure per-queue ones?
>
> > > > 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
>