We've recently debugged a huge performance degradation we were getting
on a latency sensitive workload down to the fact that libvirt is
issuing query-cpus. As it turns out, query-cpus always interrupts all
vCPU threads so that they can run ioctl to collect a number of register
information, most of which are not even used by query-cpus at all.

This series adds a new command called query-cpus-fast, which returns
the most relevant information returned by query-cpus without having
to interrupt vCPU threads. This series also updates query-cpus
documentation to advise against its use in production.

More details in individual patches.

Luiz Capitulino (2):
  qmp: add query-cpus-fast
  qmp: document query-cpus performance issue

 cpus.c               | 44 ++++++++++++++++++++++++++++++
 hmp-commands-info.hx | 14 ++++++++++
 hmp.c                | 24 +++++++++++++++++
 hmp.h                |  1 +
 qapi-schema.json     | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 158 insertions(+)

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2.14.3