Re: [PATCH v3 1/3] qmp: Support for querying stats

[Daniel P . Berrangé]

On Thu, Feb 03, 2022 at 12:12:57PM -0600, Mark Kanda wrote:
> Thanks Daniel,
> 
> On 2/1/2022 6:08 AM, Daniel P. Berrangé wrote:
> > > +#
> > > +# Since: 7.0
> > > +##
> > > +{ 'enum' : 'StatType',
> > > +  'data' : [ 'cumulative', 'instant', 'peak',
> > > +             'linear-hist', 'log-hist', 'unknown' ] }
> > IMHO 'unknown' shouldn't exist at all.
> > 
> 
> I added the 'unknown' member here (and in other enums) to handle situations
> where QEMU is behind KVM in terms of enumerating the various stat types,
> units, etc. I feel this will be a semi-common scenario (old QEMU on a new
> kernel) and with 'unknown', QEMU can at least display the raw data.
> 
> That said, I happy skip 'unknown' entries if you think that's better.

Yep, I don't think we should be including 'unknown' stuff.

An application could use this, and then we add support for the
new type and the application will now break with new QEMU because
it is presented in QMP in a different way.

The same for the 'unknown' base and unit too for that matter.


Regards,
Daniel
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