On Fri, Feb 02, 2018 at 03:07:18PM +0000, Daniel P. Berrangé wrote: > On Fri, Feb 02, 2018 at 12:50:14PM -0200, Eduardo Habkost wrote: > > (CCing qemu-devel) > > > > On Fri, Feb 02, 2018 at 09:21:59AM -0500, Luiz Capitulino wrote: > > > On Fri, 2 Feb 2018 14:19:38 +0000 > > > Daniel P. Berrangé <berrange@xxxxxxxxxx> wrote: > > > > On Fri, Feb 02, 2018 at 12:15:54PM -0200, Eduardo Habkost wrote: > > [...] > > > > > It would be also interesting to update QEMU QMP documentation to > > > > > clarify the arch-specific semantics of "halted". > > > > > > > > Any also especially clarify the awful performance implications of running > > > > this particular query command. In general I would not expect query-xxx > > > > monitor commands to interrupt all vcpus, so we should clearly warn about > > > > this ! > > > > > > Or deprecate it... > > > > We could deprecate the expensive fields on query-cpus, and move > > them to a more expensive query-cpu-state command. I believe most > > users of query-cpus are only interested in qom_path, thread_id, > > and topology info. > > > > Markus, Eric: from the QAPI point of view, is it OK to remove > > fields between QEMU versions, as long as we follow our > > deprecation policy? > > I would expect that to not be OK. A fully backwards compatible way to > deal with this would just be to add a flag to the query-cpus command > eg something like > > query-cpus arch-specific=false > > to turn off all this arch specific state, and just report the cheap > generic info. If it defaults to arch-specific=true when omitted, then > there's no compat problems. This would work, too. I would name it "full-state", "extended-state" or something similar, though. Not all arch-specific data is expensive to fetch, and not all non-arch-specific data is unexpensive. But I'd like to confirm if it's OK to make existing non-optional struct fields optional in the QAPI schema. Markus, Eric? -- Eduardo
