Eduardo Habkost <ehabk...@redhat.com> writes: > On Tue, May 23, 2017 at 04:12:43PM +0200, Markus Armbruster wrote: >> Eduardo Habkost <ehabk...@redhat.com> writes: >> >> > This series adds 'abstract' and 'parent-types' fields to the >> > output of qom-list-types. >> >> Peeking at PATCH 3, it looks like 'parent-types' is the transitive >> closure of the single direct parent type (TypeImpl member parent_type). >> Do we need information on interfaces as well? > > I think we should, but it is more complex so I plan to do in a > separate patch.
Okay. >> > For reference, below are the sizes of the output of >> > "qom-list-types abstract=true" on qemu-system-x86_64, before and >> > after applying the patches: >> > >> > * before: 11724 bytes >> > * with 'abstract' field: 20119 bytes >> > * with 'abstract' and 'parent-types': 44383 bytes >> >> Obvious ways to save space: >> >> * Make 'abstract' optional, default to false, present only when >> necessary (79 out of 456 times right now) > > Good idea. > >> >> * Pare down 'parent-types' to *direct* parent types. The indirect ones >> are redundant. > > On the one hand, I assume clients don't care if a given type is a > direct parent or indirect parent, and including only the direct > parent type will require them to make extra queries. Given the direct parents, computing their transitive closure is trivial. So a single query should suffice. > On the other hand, if the client wants to save a few queries it > can use the "implements" argument, already? Not sure. > >> >> A less obvious way: >> >> * 'parent-types' defines a relation with adjacency lists. If the >> relation is tree-shaped, we can send the tree instead, i.e. a tree of >> device names rather than list of (device name, adjacency list). New >> command unless we're willing to break qom-list-types. >> >> > I'm not sure if extending qom-list-types with this info is the >> > right way to go, or if we should keep qom-list-types as-is and >> > add a new "query-qom-type" QMP command to query info on one QOM >> > type at a time. >> >> Might lead to more traffic rather than less. Depends on what >> information the client needs to query. > > I think queries that return all available QOM types are likely to > (should?) be cached by clients. Perhaps libvirt developers can help us here. > I believe the size will stay > acceptable if we implement the two suggestions above. Please do.