On Fri, Aug 04, 2023 at 02:39:15PM +0100, Daniel P. Berrangé wrote: > On Wed, Jul 26, 2023 at 11:12:31AM -0400, Peter Xu wrote: > > On Wed, Jul 26, 2023 at 08:21:35AM +0200, Markus Armbruster wrote: > > > Peter Xu <pet...@redhat.com> writes: > > > > > > > Hi, Markus, > > > > > > > > On Tue, Jul 25, 2023 at 01:10:01PM +0200, Markus Armbruster wrote: > > > > > > [...] > > > > > > >> For better or worse, we duplicate full documentation between > > > >> MigrationParameter, MigrateSetParameters, and MigrationParameters. > > > >> This > > > >> would be the first instance where we reference instead. I'm not > > > >> opposed > > > >> to use references, but if we do, I want them used consistently. > > > > > > > > We discussed this over the other "switchover" parameter, but that > > > > patchset > > > > just stranded.. > > > > > > > > Perhaps I just provide a pre-requisite patch to remove all the comments > > > > in > > > > MigrateSetParameters and MigrationParameters, letting them all point to > > > > MigrationParameter? > > > > > > Simplifies maintaining the doc commments. But how does it affect the > > > documentation generated from it? Better, neutral, or worse? > > > > Probably somewhere neutral. There are definitely benefits, shorter > > > > man/html page in total, and avoid accidentally different docs over the same > > fields. E.g., we sometimes have different wordings for different objects: > > > > max-cpu-throttle > > maximum cpu throttle percentage. Defaults to 99. (Since 3.1) > > > > max-cpu-throttle: int (optional) > > maximum cpu throttle percentage. The default value is 99. > > (Since 3.1) > > > > This one is fine, but it's just very easy to leak in something that shows > > differently. It's good to provide coherent documentation for the same > > fields over all three objects. > > Do we have any actual problems though where the difference in > docs is actively harmful ? I agree there's a possbility of the > duplication being problematic, but unless its actually the > case in reality, it is merely a theoretical downside. > > IMHO for someone consuming the docs, this patch is worse, not neutral.
I agree. > > > > > When looking at qemu-qmp-ref.7, it can be like this when we can invite the > > reader to read the other section (assuming we only keep MigrationParameter > > to keep the documentations): > > > > MigrationParameters (Object) > > > > The object structure to represent a list of migration parameters. > > The optional members aren't actually optional. For detailed > > explanation for each of the field, please refer to the documentation > > of MigrationParameter. > > > > But the problem is we always will generate the Members entry, where now > > it'll all filled up with "Not documented".. > > > > Members > > announce-initial: int (optional) > > Not documented > > > > announce-max: int (optional) > > Not documented > > > > announce-rounds: int (optional) > > Not documented > > > > [...] > > > > I think maybe it's better we just list the members without showing "Not > > documented" every time for the other two objects. Not sure whether it's an > > easy way to fix it, or is it a major issue. > > > > For developers, dedup the comment should always be a win, afaict. > > IMHO that's optimizing for the wrong people and isn't a measurable > win anyway. Someone adding a new parameter can just cut+paste the > same docs string in the three places. It is a cost, but it is a > small one time cost, where having "not documented" is a ongoing > cost for consumers of our API. > > I don't think the burden on QEMU maintainers adding new migration > parameters is significant enough to justify ripping out our existing > docs. I had that strong feeling mostly because I'm a migration developer and migration reviewer, so I suffer on both sides. :) I was trying to stand out for either any future author/reviewer from that pov, but I think indeed the ultimate consumer is the reader. Fundamentally to solve the problem, maybe we must dedup the objects rather than the documents only? I'll try to dig a bit more in this area next week if I have time, any link for previous context would be welcomed (or obvious reason that we just won't be able to do that; I only know that at least shouldn't be trivial to resolve). For this one - Markus, let me know what do you think, or I'll simply repost v3 with the duplications (when needed, probably later not sooner). Thanks, -- Peter Xu