Am 29.09.2016 um 10:14 schrieb Daniel P. Berrange: > On Thu, Sep 29, 2016 at 10:16:41AM +1000, David Gibson wrote: >> QOM has the concept of both "object class" properties and "object >> instance" properties. >> >> The accessor functions installed for the rarely-used class properties >> still take an Object *, so the *value* of such properties is still >> per-instance; it's just the *existence* (and type) of the property >> that is per-class. > > Yes, of course. This is the whole point of class properties. It avoids > allocating the same ObjectProperty struct against every object instance > which wastes massive amounts of memory in scenarios where there are lots > of instances created.
+1 >> Of course, that's also true in practice for the great majority of >> "instance" properties, because they're created identically and >> unconditionally for every instance from the per-class instance_init >> hook. >> >> This also means that the (unused) object_class_property_add_*_ptr() >> functions don't make a lot of sense, since they require a fixed >> pointer which means the value of such a property would only be >> per-class. >> >> Given that, is there really any value to supporting the "class" >> properties in addition to the "instance" properties? This series is >> an RFC which removes all support for class properties, changing the >> few existing users to instance properties instead. >> >> Alternatively, if we *don't* want to remove class properties, should >> we instead be trying to convert the many, many "instance" properties >> whose existence is actually per-class to be class properties? > > Practically all instances properties should become class properties > as its going to save wasting memory once most are converted. Not all, but most. child<> properties were the reason to have properties on the instance. Regards, Andreas -- SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg)
