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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jun 12, 2023 at 07:27:15PM +0800, Xuan Zhuo wrote:
> On Mon, 12 Jun 2023 02:25:42 -0400, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > On Mon, Jun 12, 2023 at 02:12:35PM +0800, Xuan Zhuo wrote:
> > > We hope to support device custom counter. That is, virtio spec provides a
> > > channel for driver and device, and both key and value are provided by device.
> > >
> > > We discussed this issue earlier, and after some internal practice, I think it is
> > > still necessary to discuss this again.
> > >
> > > It is very important, each cloud vendor will always have some special counters,
> > > these counters may not exist in another vendor. At the same time, if we have
> > > to discuss it in the spec every time we add a counter, or add a feature, I
> > > think it is very inconvenient. Manufacturers may add some new counters at any
> > > time based on some new requirements. Some counters may also be removed at any
> > > time.
> > >
> > > Of course I know that doing this might hurt migration. But what I want to say is,
> > > why does it affect live migration? These counters we plan to give to users
> > > through ethtool -S, and some changes have taken place in the ethtool counters
> > > output by users. Does this have any practical impact? Or do we directly use
> > > some other output in a way, we can clearly tell the user that these counters
> > > may change during the migration process. For example, the driver is migrated
> > > to some new devices. These devices support some new counters. I think users
> > > should be able to see these new counters. These new counters may be the
> > > purpose of the migration.
> > >
> > > We don't need to support live migration at this point.
> > >
> > > Thanks.
> >
> >
> > Why not just document the thing?
> 
> Device Counter or Device Stat, we discussed this issue earlier,
> So I want to slove the problem migration firstly.
> 
> 
> Thanks.

Sorry have trouble parsing this.

Can we get examples of counters from various vendors, so that
it's clear what kind of thing this, and it becomes convincing
that abstracting this in virtio spec is pointless?

Also, am I right assuming that in virtualized settings this is mostly
relevant for hosts? E.g. guests see a vendor neutral virtio but
host wants to figure out source of issues?




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