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[libvirt] [RFC PATCH 0/8 v2] Summary on block IO throttle

Changes since V1
 - Implement the support to get the block io throttling for 
   a device as read only connection - QMP/HMP.
 - Split virDomainBlockIoThrottle into two separate functions
     virDomainSetBlockIoThrottle - Set block I/O limits for a device
      - Requires a connection in 'write' mode.
      - Limits (info) structure passed as an input parameter
     virDomainGetBlockIoThrottle - Get the current block I/O limits for a device
      - Works on a read-only connection.
      - Current limits are written to the output parameter (reply).
 - And Other fixups suggested by Adam Litke, Daniel P. Berrange.
   - For dynamically allocate the blkiothrottle struct, I will fix
     it when implement --current --live --config options support.

Today libvirt supports the cgroups blkio-controller, which handles
proportional shares and throughput/iops limits on host block devices.
blkio-controller does not support network file systems (NFS) or other
QEMU remote block drivers (curl, Ceph/rbd, sheepdog) since they are
not host block devices. QEMU I/O throttling works with all types of
drive and can be applied independently to each drive attached to
a guest and supports throughput/iops limits.

To help add QEMU I/O throttling support to libvirt, we plan to complete
it with add new API virDomainBlockIoThrottle(), new command 'blkiothrottle'
and Python bindings.

Notes: we are sending this series out now(even though they are not completed
yet.)because we want to start the review process. #1)#2) features were implemented
by Zhi Yong Wu:

1) Enable the blkio throttling in xml when guest is starting up.

Add blkio throttling in xml as follows:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/kvm-one.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
      <iotune bps='n'.../>

2) Enable blkio throttling setting at guest running time.

virsh blkiothrottle <domain> <device> [--bps<number>] [--bps_rd<number>] \
[--bps_wr<number>] [--iops<number>] [--iops_rd<number>] [--iops_wr<number>]

3) The support to get the current block i/o throttling for a device - HMP/QMP.

virsh blkiothrottle <domain> <device>

And I will address feedback and work on the missing features in few days includes:

4) Python binding support for setting blkio throttling.
5) --current --live --config options support to unify the libvirt API.

 daemon/remote.c                 |   85 +++++++++++++++++
 include/libvirt/libvirt.h.in    |   25 +++++
 python/generator.py             |    2 +
 python/libvirt-override-api.xml |   16 ++++
 python/libvirt-override.c       |   43 +++++++++
 src/conf/domain_conf.c          |   77 ++++++++++++++++
 src/conf/domain_conf.h          |   11 +++
 src/driver.h                    |   18 ++++
 src/libvirt.c                   |  120 ++++++++++++++++++++++++
 src/libvirt_public.syms         |    2 +
 src/qemu/qemu_command.c         |   35 +++++++
 src/qemu/qemu_driver.c          |  108 ++++++++++++++++++++++
 src/qemu/qemu_monitor.c         |   36 ++++++++
 src/qemu/qemu_monitor.h         |   10 ++
 src/qemu/qemu_monitor_json.c    |  191 +++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_monitor_json.h    |   10 ++
 src/qemu/qemu_monitor_text.c    |   88 ++++++++++++++++++
 src/qemu/qemu_monitor_text.h    |   10 ++
 src/remote/remote_driver.c      |   81 +++++++++++++++++
 src/remote/remote_protocol.x    |   39 ++++++++-
 src/remote_protocol-structs     |   34 +++++++
 src/util/xml.h                  |    3 +
 tools/virsh.c                   |  100 ++++++++++++++++++++
 tools/virsh.pod                 |   13 +++
 24 files changed, 1156 insertions(+), 1 deletions(-)


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