VMSVGA extremely laggy keyboard input for Linux guests

[Artem S. Tashkinov]

Pretty much all Linux guests with this video adapter have an extremely laggy and random keyboard input: while you're typing in any graphical terminal sometimes what you're typing instantly shows on the screen, sometimes there's a random delay for up to three seconds.

It's annoying and maddening.

Host OS: Fedora 33, Linux 5.14.3
Environment: XFCE with no compositing
CPU: Ryzen 7 5800X
Guest OS: any modern Linux OS without 3D acceleration

Changing the amount of video memory from default 16MB to 128MB makes the issue less pronounced but it's still there.

VBoxSVGA is more or less free from this issue. Keyboard input is not perfect (there's quite a considerable input lag) but at least it's not as bad as with VMSVGA.

[fth0]

I think that Monitor Count, display resolution(s) and Scale Factor also play a role ...

[Codehunter]

I agree. All three VGraphics has more or less performance issues. See #20089 from me. If you have an R7-5800X i think you has an physical Graphics card. When its a Nvidia with Noveau driver, this is possibly the bottleneck. Please have a look on ​https://www.phoronix.com/scan.php?page=article&item=nvidia-nouveau-2019&num=1

But in general, i think there is a lot of work to do on the VGraphics front. At the moment i switched back because VBoxSVGA is much more laggy than VBoxVGA and VMSVGA is completely useless on my machine (R7-2700X, NV GT1030, 32 GB RAM).

At the moment, i cant say why this is. The only thing i know is, that VGraphics in VBox on Ryzen with Nvidia graphics are a mess.

PS: I'm on Linux Mint 19.2 Host. Here i have added the "CPU load desklet" to the desktop and configured it to a 1 second refresh interval. Here i can see that one core does permanently peaks up to 100% when VBox is configured to two screens and both are turned into seamless mode. When the VM is stuttering and the keyboard input is laggy/randomized, the host CPU load is growing more and more until the VM freezes. Then I must kill the VM process and restart it.