When I am installing windows or linux with virt-manage2.0,the VM is running very very slow? about virt-manager HOT 6 OPEN

Hi, can you please provide your host OS and if possible debug logs from virt-manager. You can run it from terminal using virt-manager --debug.

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@feici03 Can you please provide more details about your distribution, what steps are you doing and if possible debug logs from virt-manager.

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For the record, I was also experiencing substantial slowdown when running in fullscreen mode with my settings. I think it was tied directly to my VM settings, however. Since the original poster didn't add details for their setup, here was mine:
virt-manager-debug-240413.txt

What I found was that QXL in general was slower and had abysmal performance when in fullscreen mode. Switching Spice to Display Server Listen Type Address and the graphics driver to virtio improved performance. The reason I was looking into this was because Fedora KDE had a user report sluggish behaviour in their VMs after upgrading to Plasma 6 (Fedora 40). I tested a new VM in Gnome Boxes vs Virt-Manager and also found Gnome Boxes had better performance at first. After matching settings in virt-manager to what Gnome Boxes had in their settings, my performance in virt-manager essentially matched.

I've forwarded the original poster to this post since after matching settings, I wasn't able to duplicate their performance issues.

Host Details:

Operating System: Fedora Linux 40 (KDE)
KDE Plasma Version: 6.0.3
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.2
Kernel Version: 6.8.4-300.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 2700X Eight-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 590 Series
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: X470 AORUS GAMING 7 WIFI

from virt-manager.

Same problem here as described by @timaeos

Details of host machine running virt-manager 4.1.0:

• Fedora 40
• Plasma 6.0.3 on Wayland
• GPU: AMD Radeon RX480
• CPU: Ryzen 5 3600
• RAM: 128 GB
• kernel: 6.8.1-300.fc40.x86_64

virt-manager_debug.txt

from virt-manager.

I'm not sure if both of you are hitting the same issue as original poster that mentioned virt-manager 2.0 which is pretty old and the issue they have could be completely different.

Now for the issue reported by @timaeos and @Germano0 I'm guessing that your VMs are not windows VMs if Gnome boxes used virtio video by default as for windows it would use QXL.

I did bit of testing and on my host with monitor that has resolution 3440 x 1440 with Fedora KDE VM. First I tired using QXL video and when switching to fullscreen mode I was not able to match my host resolution inside the VM. So I change the video to virtio and started the VM again and I was able to match my host resolution in fullscreen mode and it felt ok with performance.

So as the next step I did change back to QXL video and switched to the XML tab and changed vgamem to 65536 so the XML looked like this:

<model type="qxl" ram="65536" vram="65536" vgamem="65536" heads="1" primary="yes"/>

and started the VM again. After this change I was able to match the host resolution in fullscreen mode and the VM felt OK.

Would you be able to try QXL video with more memory to see if it feels slow or not?

How did you install the VM with virt-manager and when? When I tried to create a new VM using Fedora 40 beta iso image it got detected as Fedora and the default video device was virtio.

from virt-manager.

Same problem with Spice for proxmox
Spice is very, very slow, not usable. noVNS woks fine, as long as no Spice client is using the proxmox VM. If I change the proxmox Hardware Display Option to VirtlO-GPU (from Spice), it is a bit faster. However I did not check if sound and USB transfer works with VirtlO-GPU.

I use proxmox 7.4.
proxmox guest is ZorinOS.
On the client (Ubuntu 22.04 LTS) is use Virtual Machine Viewer 7.0, which is in fact virt-manager, I believe.

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