Re: [PATCH v3 2/3] util/main-loop: Introduce the main loop into QOM

[Nicolas Saenz Julienne]

Hi Markus,

On Wed, 2022-03-16 at 15:28 +0100, Markus Armbruster wrote:
> Nicolas Saenz Julienne <nsaenzju@redhat.com> writes:
> 
> > 'event-loop-base' provides basic property handling for all 'AioContext'
> > based event loops. So let's define a new 'MainLoopClass' that inherits
> > from it. This will permit tweaking the main loop's properties through
> > qapi as well as through the command line using the '-object' keyword[1].
> > Only one instance of 'MainLoopClass' might be created at any time.
> > 
> > 'EventLoopBaseClass' learns a new callback, 'can_be_deleted()' so as to
> > mark 'MainLoop' as non-deletable.
> > 
> > [1] For example:
> >       -object main-loop,id=main-loop,aio-max-batch=<value>
> > 
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> 
> [...]
> 
> > diff --git a/qapi/qom.json b/qapi/qom.json
> > index eeb5395ff3..10800166e8 100644
> > --- a/qapi/qom.json
> > +++ b/qapi/qom.json
> > @@ -528,6 +528,19 @@
> >              '*poll-shrink': 'int',
> >              '*aio-max-batch': 'int' } }
> >  
> > +##
> > +# @MainLoopProperties:
> > +#
> > +# Properties for the main-loop object.
> > +#
> > +# @aio-max-batch: maximum number of requests in a batch for the AIO engine,
> > +#                 0 means that the engine will use its default (default:0)
> > +#
> > +# Since: 7.1
> > +##
> > +{ 'struct': 'MainLoopProperties',
> > +  'data': { '*aio-max-batch': 'int' } }
> > +
> 
> IothreadProperties has the same member, with the same documentation.
> 
> Do main loop and iothreads have a common ancestor, conceptually?
>
> If yes, it might make sense for MainLoopProperties and
> IothreadProperties to have a common base type, and put @aio-max-batch
> there.  This is not a demand.

Yes it could make sense, in terms of the QOM they both inherit from the same
base abstract class, called EventLoopBase.

On top of that, patch #3 adds two more common properties. So doing so would
avoid some amount of duplication. I'll look into it and prepare a v4 of the
series.

Thanks!

-- 
Nicolás Sáenz