Re: [Qemu-devel] [PATCH v13 01/14] qobject: Simplify QObject

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> The QObject hierarchy is small enough, and unlikely to grow further
> (since we only use it to map to JSON and already cover all JSON
> types), that we can simplify things by not tracking a separate
> vtable, but just inline the refcnt element of the vtable QType
> directly into QObject, and track a separate array of destroy
> functions.  We can drop qnull_destroy_obj() in the process.

Make that something like "inline the code element of the vtable QType
directly into QObject (renamed to type), and".

>
> The remaining QObject subclasses must export their destructor.
>
> This also has the nice benefit of moving the typename 'QType'
> out of the way, so that the next patch can repurpose it for a
> nicer name for 'qtype_code'.
>
> The various objects are still the same size (so no change in cache
> line pressure), but now have less indirection (although I didn't
> bother benchmarking to see if there is a noticeable speedup, as
> we don't have hard evidence that this was in a performance hotspot
> in the first place).
>
> Suggested-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Eric Blake <eblake@redhat.com>