[libvirt] cannot get all memory stats for domain

ShadowLim · 2017-07-18 19:56:08

Hello everyone.
I'm experiencing some problems with virtual machine (guest windows 7, x86_64), running under qemu-kvm and managed by libvirt (created and ran mostly from virt-manager). The problem is that I cannot get full memory statistics either from running

virsh -c qemu:///system dommemstat win7

or by calling the

virDomainMemoryStats(...)

from c++ code (which is, as far as I understood, more or less same things). I also tested libvirt 35th example from libvirt aplication dev guide. This really concerns me, because right now I am working under project, aimed to auto-set the optimal size of memory for vm and hence I need them in my code.
The only output I get from the virsh is

actual 4194304
last_update 1500404513
rss 4161676

After searching the web I found out that these are the stats, which libvirt can obtain without applying to ballooning driver. However I already installed VirtIO ballooning driver in windows and the system claims that it is running. I don't really know, how to find out whether the qemu is aware of it or not (opened for your ideas).
Also I found that I need to set statistics period in the system xml, which I already did and which gave nothing. I also found out that qemu uses some "qom-get" script to actually measure stats, but I cannot use it from

virsh # qemu-monitor-command 1 --hmp "qom-get"

(outputs that command is unknown) and I cannot see it in my PATH. Also

pacman -Fo qom-get

and

pkgfile qom-get

give nothing.
My host system is Arch Linux. The contents of the win7.xml are

<domain type='kvm'>
<name>win7</name>
<uuid>438145c1-a2df-4c86-96d6-2bf7b379d70b</uuid>
<memory unit='KiB'>4194304</memory>
<currentMemory unit='KiB'>4194304</currentMemory>
<vcpu placement='static' current='2'>4</vcpu>
<os>
<type arch='x86_64' machine='pc-i440fx-2.9'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<hyperv>
<relaxed state='on'/>
<vapic state='on'/>
<spinlocks state='on' retries='8191'/>
</hyperv>
<vmport state='off'/>
</features>
<cpu mode='custom' match='exact' check='partial'>
<model fallback='allow'>Broadwell-noTSX</model>
</cpu>
<clock offset='localtime'>
<timer name='rtc' tickpolicy='catchup'/>
<timer name='pit' tickpolicy='delay'/>
<timer name='hpet' present='no'/>
<timer name='hypervclock' present='yes'/>
</clock>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<pm>
<suspend-to-mem enabled='no'/>
<suspend-to-disk enabled='no'/>
</pm>
<devices>
<emulator>/usr/sbin/qemu-system-x86_64</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/var/lib/libvirt/images/win7.qcow2'/>
<target dev='hda' bus='ide'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<target dev='hdb' bus='ide'/>
<readonly/>
<address type='drive' controller='0' bus='0' target='0' unit='1'/>
</disk>
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/usr/share/virtio/virtio-win.iso'/>
<target dev='hdc' bus='ide'/>
<readonly/>
<address type='drive' controller='0' bus='1' target='0' unit='0'/>
</disk>
<controller type='usb' index='0' model='ich9-ehci1'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x7'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci1'>
<master startport='0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci2'>
<master startport='2'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/>
</controller>
<controller type='usb' index='0' model='ich9-uhci3'>
<master startport='4'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'/>
<controller type='ide' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<controller type='virtio-serial' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</controller>
<interface type='network'>
<mac address='52:54:00:9d:4e:85'/>
<source network='default'/>
<model type='rtl8139'/>
<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>
<channel type='spicevmc'>
<target type='virtio' name='com.redhat.spice.0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>
<input type='tablet' bus='usb'>
<address type='usb' bus='0' port='1'/>
</input>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<graphics type='spice' autoport='yes'>
<listen type='address'/>
<image compression='off'/>
</graphics>
<sound model='ich6'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</sound>
<video>
<model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<redirdev bus='usb' type='spicevmc'>
<address type='usb' bus='0' port='2'/>
</redirdev>
<redirdev bus='usb' type='spicevmc'>
<address type='usb' bus='0' port='3'/>
</redirdev>
<memballoon model='virtio'>
<stats period='10'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</memballoon>
</devices>
</domain>

I am definitely missing something, but I cannot see what. Could anyone, please, give me any useful links or guides? I would really appreciate it.
I think that I am going to send duplicate of this issue to Stack Overflow. If anyone will give the appropriate answer, I will share it with the other site.
================================================

UPD. balloon is working: I can do such things as

virsh # qemu-monitor-command win7 --hmp "info balloon"
balloon: actual=4096
virsh # qemu-monitor-command win7 --hmp "balloon 2048"
virsh # qemu-monitor-command win7 --hmp "info balloon"
balloon: actual=2048

But the qom-get won't do:

virsh # qemu-monitor-command windows7 '{ "execute": "qom-get",  "arguments": { "path": "/machine/peripheral/balloon0",  "property": "guest-stats" } }'
{"return":{"stats":{"stat-swap-out":-1,"stat-available-memory":-1,"stat-free-memory":-1,"stat-minor-faults":-1,"stat-major-faults":-1,"stat-total-memory":-1,"stat-swap-in":-1},"last-update":1500639136},"id":"libvirt-396"}

Help would be much appreciated.

Last edited by ShadowLim (2017-07-21 12:28:15)

ShadowLim · 2017-07-25 11:25:52

The problem was that the Balloon service wasn't installed properly. If you face same problem, possible solution will be to open command line, go to the CD-ROM with VirtIO drivers, go to Balloon directory and deeper, depending on your system and architecture. When you are in amd64 (x86) directory, type

blnsrv.exe -i

and the service should install itself. After that the problem will be gone (at least, this worked for me).

Arch Linux

#1 2017-07-18 19:56:08

[libvirt] cannot get all memory stats for domain

#2 2017-07-25 11:25:52

Re: [libvirt] cannot get all memory stats for domain

Board footer