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High Stuttering in Windows VM Game, and none in Bare metal


sonuyos

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I am facing stuttering in game, on Windows VM.

 

Currently was playing Kena Bridge of Spirits. In Windows VM, i get 56 fps (as i have it locked at 56 due to freesync), however my 1% lows are pretty freaking low, about 20-30fps, which really ruins the experience, and this happens in all the games, i was playing Deathloop yesterday and same.

 

When i switched to Bare metal (booted directly off the SSD), i get 56 locked, and my 1% lows arent going below 55, which is really really stable and crazy to see the difference.

 

Please help me.

 

I have attached my KVM config. and server config.

 

PS: No docker is running while i performed the test and the CPU was very stable in both conditions. I roamed only at a specific location to do the test and it was identical.

 

I am facing this issue from day one, and was just making it work somehow, but it is really jaring.

 

Also i noticed some flicking of the screen too while gaming (could be freesync flickering?) which i (as far as i remember), did not see in baremetal.

 

<?xml version='1.0' encoding='UTF-8'?>
<domain type='kvm' id='5'>
  <name>Windows 10 - 2020</name>
  <uuid>e35942b5-aa7d-461b-6d58-64f3e347626a</uuid>
  <metadata>
    <vmtemplate xmlns="unraid" name="Windows 10" icon="windows.png" os="windows10"/>
  </metadata>
  <memory unit='KiB'>26214400</memory>
  <currentMemory unit='KiB'>26214400</currentMemory>
  <memoryBacking>
    <nosharepages/>
  </memoryBacking>
  <vcpu placement='static'>14</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='1'/>
    <vcpupin vcpu='1' cpuset='9'/>
    <vcpupin vcpu='2' cpuset='2'/>
    <vcpupin vcpu='3' cpuset='10'/>
    <vcpupin vcpu='4' cpuset='3'/>
    <vcpupin vcpu='5' cpuset='11'/>
    <vcpupin vcpu='6' cpuset='4'/>
    <vcpupin vcpu='7' cpuset='12'/>
    <vcpupin vcpu='8' cpuset='5'/>
    <vcpupin vcpu='9' cpuset='13'/>
    <vcpupin vcpu='10' cpuset='6'/>
    <vcpupin vcpu='11' cpuset='14'/>
    <vcpupin vcpu='12' cpuset='7'/>
    <vcpupin vcpu='13' cpuset='15'/>
    <emulatorpin cpuset='1,9'/>
  </cputune>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-5.1'>hvm</type>
    <loader readonly='yes' type='pflash'>/usr/share/qemu/ovmf-x64/OVMF_CODE-pure-efi.fd</loader>
    <nvram>/etc/libvirt/qemu/nvram/acbbb949-4b67-7893-98bb-02fa4d5f218a_VARS-pure-efi.fd</nvram>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vendor_id state='on' value='none'/>
    </hyperv>
  </features>
  <cpu mode='host-passthrough' check='none' migratable='on'>
    <topology sockets='1' dies='1' cores='7' threads='2'/>
    <cache mode='passthrough'/>
    <feature policy='require' name='topoext'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='hypervclock' present='yes'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/local/sbin/qemu</emulator>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source dev='/dev/disk/by-id/ata-WDC_WD1002FAEX-00Z3A0_WD-WCATRC635557' index='2'/>
      <backingStore/>
      <target dev='hdb' bus='sata'/>
      <alias name='sata0-0-2'/>
      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='writeback'/>
      <source dev='/dev/disk/by-id/ata-Samsung_SSD_860_EVO_500GB_S4FNNF0NB21554M' index='1'/>
      <backingStore/>
      <target dev='hdc' bus='sata'/>
      <boot order='1'/>
      <alias name='sata0-0-3'/>
      <address type='drive' controller='0' bus='0' target='0' unit='3'/>
    </disk>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='sata' index='0'>
      <alias name='sata0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </controller>
    <controller type='usb' index='0' model='nec-xhci' ports='15'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:2b:9f:b5'/>
      <source bridge='br0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </interface>
    <interface type='bridge'>
      <mac address='52:54:00:7c:a9:35'/>
      <source bridge='br1'/>
      <target dev='vnet1'/>
      <model type='virtio'/>
      <alias name='net1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x13' function='0x0'/>
    </interface>
    <interface type='bridge'>
      <mac address='52:54:00:7a:db:8f'/>
      <source bridge='virbr1'/>
      <target dev='vnet2'/>
      <model type='virtio'/>
      <alias name='net2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x14' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      </target>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <channel type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/channel/target/domain-5-Windows 10 - 2020/org.qemu.guest_agent.0'/>
      <target type='virtio' name='org.qemu.guest_agent.0' state='disconnected'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'>
      <alias name='input1'/>
    </input>
    <input type='keyboard' bus='ps2'>
      <alias name='input2'/>
    </input>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x0b' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev0'/>
      <rom file='/boot/Zotac.RTX2070.8192.181019.rom'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x0b' slot='0x00' function='0x1'/>
      </source>
      <alias name='hostdev1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
      </source>
      <boot order='2'/>
      <alias name='hostdev2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x11' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x08' slot='0x00' function='0x1'/>
      </source>
      <alias name='hostdev4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x08' slot='0x00' function='0x3'/>
      </source>
      <alias name='hostdev5'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
      </source>
      <alias name='hostdev6'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x18' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='usb' managed='no'>
      <source>
        <vendor id='0x1b1c'/>
        <product id='0x1b2d'/>
        <address bus='5' device='2'/>
      </source>
      <alias name='hostdev7'/>
      <address type='usb' bus='0' port='3'/>
    </hostdev>
    <memballoon model='none'/>
  </devices>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+0:+100</label>
    <imagelabel>+0:+100</imagelabel>
  </seclabel>
</domain>

 

tower-diagnostics-20210925-1730.zip

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  • 1 year later...

Make sure you backup your existing XML.

 

Stop the VM, edit the xml by removing multifunction on the card, remove <address> node (not <source><address>!!!), then save the xml and see if you get any improvements.

The idea is to have QEMU assign the busses for each GPU component.

 

Also, take a look at this: https://forums.guru3d.com/threads/windows-line-based-vs-message-signaled-based-interrupts-msi-tool.378044/

Run 'MSI_util_v3' and apply MSI to both GPU and GPU-Audio. This is what mine looks like:

image.png.8d5532b8bbf9fe7df458a61ec7973a1f.png

 

Also, try removing 'emulatorpin'.

 

You should also try machine type Q35.

 

You didn't mention which CPU you have, but try this feature-set:

 

  <features>
    <acpi/>
    <apic eoi='on'/>
    <hyperv mode='custom'>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vpindex state='on'/>
      <runtime state='on'/>
      <synic state='on'/>
      <stimer state='on'>
        <direct state='on'/>
      </stimer>
      <reset state='on'/>
      <vendor_id state='on' value='1234567890ab'/>
      <frequencies state='on'/>
      <reenlightenment state='on'/>
      <tlbflush state='on'/>
      <ipi state='on'/>
      <evmcs state='off'/>
    </hyperv>
    <kvm>
      <hidden state='on'/>
    </kvm>
    <pmu state='off'/>
    <vmport state='off'/>
    <ioapic driver='kvm'/>
  </features>

 

If QEMU complains about any of them, just remove one-by-one.

 

Also, try these cpu & clock config:

  <cpu mode='host-passthrough' check='none' migratable='off'>
    <topology sockets='1' dies='1' cores='8' threads='2'/>
    <cache mode='passthrough'/>
    <feature policy='require' name='topoext'/>
    <feature policy='require' name='invtsc'/>
    <feature policy='require' name='x2apic'/>
    <feature policy='disable' name='monitor'/>
    <feature policy='disable' name='svm'/>
    <feature policy='disable' name='hypervisor'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='pit' present='no' tickpolicy='discard'/>
    <timer name='rtc' present='no' tickpolicy='catchup'/>
    <timer name='hpet' present='no'/>
    <timer name='kvmclock' present='no'/>
    <timer name='hypervclock' present='yes'/>
    <timer name='tsc' present='yes' mode='native'/>
  </clock>

 

Add this block before </devices> tag:

<memballoon model='none'/>

 

Again, remove any item that QEMU complains about.

 

Finally, if you want resizable-BAR to work in a VM, you need to add the following block at the end (before </domain> tag):

  <qemu:commandline>
    <qemu:arg value='-fw_cfg'/>
    <qemu:arg value='opt/ovmf/X-PciMmio64Mb,string=65536'/>
  </qemu:commandline>

 

You might also consider using hugepages and reserving them for the VM(s).

So just try the different tweaks and see if you get any improvements.

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