On Fri, Feb 02, 2018 at 05:23:59PM +0000, Dr. David Alan Gilbert wrote: > * Eduardo Habkost (ehabkost@xxxxxxxxxx) 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. > > Would that data be available without the bql? I ask because if it is > then a small advantage to having a separate command is that the command > could be marked OOB with Peter's new series and never take the lock. We would need a mechanism to safely walk the CPU list without the BQL, so I wouldn't bother trying to make a OOB-capable version of query-cpus unless really necessary. -- Eduardo
