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

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Feb 01, 2022 at 11:51:26AM +0100, Paolo Bonzini wrote:
> On 1/31/22 20:43, Mark Kanda wrote:
> > 
> > { "execute": "query-stats", "arguments" : { "target": "vm" } }
> > { "return": {
> >      "list": [
> >        { "provider": "kvm",
> >          "stats": [
> >            { "name": "max_mmu_page_hash_collisions", "value": 0 },
> >            { "name": "max_mmu_rmap_size", "value": 0 },
> >            { "name": "nx_lpage_splits", "value": 131 },
> >           ...
> >          ] }
> >        { "provider": "provider XYZ",
> >        ...
> >      ],
> >      "target": "vm"
> >    }
> > }
> 
> Perhaps it's better to have a better name than "list" for clarity, like you
> already did with 'stats':
> 
> { 'struct': 'VCPUResultsEntry',
>   'data': { 'path': 'str',
>             'providers': [ 'StatsResultsEntry' ] } }
> 
> { 'struct': 'VCPUStatsResults',
>   'data': { 'objects': [ 'VCPUResultsEntry' ] } }
> 
> 
> { 'struct': 'VMStatsResults',
>   'data': { 'providers' : [ 'StatsResultsEntry' ] } }
> 
> Also, here:
> 
> > +{ 'alternate': 'StatsValue',
> > +  'data': { 'scalar': 'uint64',
> > +            'list': 'StatsValueArray' } }
> 
> is it possible to just do
> 
> { 'alternate': 'StatsValue',
>   'data': { 'scalar': 'uint64',
>             'list': ['uint64'] } }

No, the QAPI generator throws its toys out of the pram.

It claims you can have any set of data types which have a
distinct representation on the wire, so this is valid from
that POV.  Something about the parser/code generator can't
cope with this inline array though - it wants a named type
which means a built-in scalar, or a compound type, but not
an array :-(


Regards,
Daniel
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