[libvirt] [PATCH 00/11] Allow modification of IOThread polling values (redux)

[John Ferlan]

This series attempts to resurrect the concept of being able to modify
the IOThread polling parameters; however, in a slightly different
manner than the previous series posted by posted by Pavel Hrdina
<phrdina at redhat.com>:

  https://www.redhat.com/archives/libvir-list/2017-February/msg01047.html

The work is prompted by continued pleas found in the bz:

  https://bugzilla.redhat.com/show_bug.cgi?id=1545732

to provide some way to modify the paremters without needing to supply
QEMU command line pass through values.

It's accepted that the values being changed are fairly or extremely
low level type knobs; however, it's also shown that by being able to
turn the knob it is possible for certain, specific appliances to be
able to gain a performance benefit for the thread at the expense of
other competing threads.

Unlike the previous series, this series does not attempt to save the
polling values in the guest XML. Rather, it only modifies the live
guest's IOThread with new values. It also doesn't provide the polling
values in a virsh iothread* command, rather it uses the domstats
in order to fetch and display the values. The theory being this
leaves the onus on the higher level appliance/application to provide
the "proper guidance" and "concerns" related to changing the values
to the consumer. Not saving the values means whatever values that
are chosen do not "live" in perpetuity. Once the guest is shut down
or the IOThread removed from guest, the hypervisor default values
take over again. Perhaps not a perfect situation in terms of what
the bz requests; however, storage of default values that could
cause performance issues is not an optimal situation. So this I
figured is a "comprimise" of sorts.

If it's still felt that no we don't want to do this, then fine,
but please in doing so own the bz, state your case, and close it.
I'm 50/50 on it, but figured at least I'd present this option and
see what the concensus was.

John Ferlan (11):
  qemu: Check for and return IOThread polling values if available
  qemu: Split qemuDomainGetIOThreadsLive
  qemu: Implement the ability to return IOThread stats
  virsh: Add ability to display IOThread stats
  lib: Introduce virDomainSetIOThreadParams
  qemu: Add monitor functions to set IOThread params
  qemu: Alter qemuDomainChgIOThread to take enum instead of bool
  qemu: Alter qemuDomainChgIOThread to take qemuMonitorIOThreadInfo
  qemu: Detect whether iothread polling is supported
  qemu: Introduce qemuDomainSetIOThreadParams
  tools: Add virsh iothreadset command

 include/libvirt/libvirt-domain.h              |  45 ++
 src/driver-hypervisor.h                       |   8 +
 src/libvirt-domain.c                          | 109 +++++
 src/libvirt_public.syms                       |   5 +
 src/qemu/qemu_capabilities.c                  |   2 +
 src/qemu/qemu_capabilities.h                  |   1 +
 src/qemu/qemu_driver.c                        | 393 ++++++++++++++++--
 src/qemu/qemu_monitor.c                       |  19 +
 src/qemu/qemu_monitor.h                       |   6 +
 src/qemu/qemu_monitor_json.c                  |  48 +++
 src/qemu/qemu_monitor_json.h                  |   4 +
 src/remote/remote_driver.c                    |   1 +
 src/remote/remote_protocol.x                  |  21 +-
 src/remote_protocol-structs                   |  10 +
 .../caps_2.10.0.aarch64.xml                   |   1 +
 .../caps_2.10.0.ppc64.xml                     |   1 +
 .../caps_2.10.0.s390x.xml                     |   1 +
 .../caps_2.10.0.x86_64.xml                    |   1 +
 .../caps_2.11.0.s390x.xml                     |   1 +
 .../caps_2.11.0.x86_64.xml                    |   1 +
 .../caps_2.12.0.aarch64.xml                   |   1 +
 .../caps_2.12.0.ppc64.xml                     |   1 +
 .../caps_2.12.0.s390x.xml                     |   1 +
 .../caps_2.12.0.x86_64.xml                    |   1 +
 .../qemucapabilitiesdata/caps_2.9.0.ppc64.xml |   1 +
 .../qemucapabilitiesdata/caps_2.9.0.s390x.xml |   1 +
 .../caps_2.9.0.x86_64.xml                     |   1 +
 .../qemucapabilitiesdata/caps_3.0.0.ppc64.xml |   1 +
 .../caps_3.0.0.riscv32.xml                    |   1 +
 .../caps_3.0.0.riscv64.xml                    |   1 +
 .../qemucapabilitiesdata/caps_3.0.0.s390x.xml |   1 +
 .../caps_3.0.0.x86_64.xml                     |   1 +
 tools/virsh-domain-monitor.c                  |   7 +
 tools/virsh-domain.c                          | 110 +++++
 tools/virsh.pod                               |  47 ++-
 35 files changed, 810 insertions(+), 44 deletions(-)

-- 
2.17.1