[Qemu-devel] Cannot add iothreads label in libvirt xml configuration file

[Weiwei Jia]

Hi,

I cannot add iothreads
(https://libvirt.org/formatdomain.html#elementsIOThreadsAllocation) in
the libvirt xml configuration file. Once I add
"<iothreads>4</iothreads>" and other related config for IOthreads into
the libvirt xml configuration file with virsh command and save it,
these iothreads related configuration will disappear after I open
libvirt xml configuration file again for double-check.

The current libvirt xml configuration file is like following.

# virsh dumpxml kvm1
<domain type='kvm'>
  <name>kvm1</name>
  <uuid>20811918-9057-4496-aa03-0fe9d1bcaf78</uuid>
  <memory unit='KiB'>8194304</memory>
  <currentMemory unit='KiB'>8194304</currentMemory>
  <vcpu placement='static'>6</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='1'/>
    <vcpupin vcpu='2' cpuset='2'/>
    <vcpupin vcpu='3' cpuset='3'/>
    <vcpupin vcpu='4' cpuset='4'/>
    <vcpupin vcpu='5' cpuset='5'/>
    <emulatorpin cpuset='12-15'/>
  </cputune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-2.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm-spice</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source file='/var/lib/libvirt/images/kvm1.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
function='0x0'/>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' target='0' unit='0'/>
    </disk>
    <controller type='usb' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'/>
    <controller type='scsi' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x0'/>
    </controller>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x1'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:a7:67:eb'/>
      <source network='default'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>
    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='none'/>
</domain>





I want to config above xml file to be like following but once I save
it, the iothreads related configuration will disappear (like above)
after I re-open the libvirt xml for double-check.

<domain  type='kvm' id='1'
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>kvm1</name>
  <memory unit='KiB'>8194304</memory>
  <currentMemory unit='KiB'>8194304</currentMemory>
  <vcpu placement='static'>6</vcpu>
  <iothreads>4</iothreads>
  <iothreadids>
 <iothread id="2"/>
 <iothread id="4"/>
 <iothread id="6"/>
 <iothread id="8"/>
  </iothreadids>
  <cputune>
    <vcpupin vcpu='0' cpuset='0'/>
    <vcpupin vcpu='1' cpuset='1'/>
    <vcpupin vcpu='2' cpuset='2'/>
    <vcpupin vcpu='3' cpuset='3'/>
    <vcpupin vcpu='4' cpuset='4'/>
    <vcpupin vcpu='5' cpuset='5'/>
<emulatorpin cpuset="12-15"/>
<iothreadpin iothread="2" cpuset="7"/>
<iothreadpin iothread="4" cpuset="8"/>
<iothreadpin iothread="6" cpuset="9"/>
<iothreadpin iothread="8" cpuset="10"/>
  </cputune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-2.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/kvm-spice</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native' iothread='2-8'/>
 <source file='/home/wj47/ssd1/kvm1.img'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06'
function='0x0'/>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <alias name='ide0-1-0'/>
      <address type='drive' controller='0' bus='1' target='0' unit='0'/>
    </disk>
    <controller type='usb' index='0'>
      <alias name='usb0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='scsi' index='0'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04'
function='0x0'/>
    </controller>
    <controller type='ide' index='0'>
      <alias name='ide0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
function='0x1'/>
    </controller>
    <interface type='network'>
      <source network='default'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/11'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/11'>
      <source path='/dev/pts/11'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05'
function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='none'/>
</domain>





Another concern is like this: can I config 4 dedicated IOthreads for
one drive. Just like above, I want to start 4 IOthreads for
virtio-disk0. If true, is my config like above correct? Thank you.

Best,
Weiwei Jia