KVM guest CPU high, strange display issues

[Anderath]

OK, bear with me as I needed to just re-type all of this as I lost my progress from being logged out automatically.



Let me start off by letting you know how I have things setup.

I have installed ZFS on linux through the wiki's instructions:

http://pve.proxmox.com/wiki/ZFS

I've limited the amount of RAM it uses to 4096 MB and allowed it to start mounting datasets just as it would any other filesystem when proxmox starts up every time.

Besides having Htop installed, there's really nothing else custom about my proxmox installation.

I've recently switch my installation off of a little 16 GB usb drive to a 120 GB SSD and freshly restored all of my old VMs.

As you can see from the above, this happens from time to time in a newly installed Linux Mint KVM guest. KVM processes on my proxmox spike to almost full blast on all cores for some reason and my VM becomes unresponsive. And when they are able to respond, it shows randomly replaced font letters with random ASCII symbols. In the screenshot above, it decided to replace these random selections with just blank spaces.

I can reproduce this as all it takes is attempting to use the VM for a solid 15-30 minutes or sometimes every 5 minutes. It happens in both Spice and Novnc displays.

I love proxmox but it has been my only experience with KVM virtualization and I'm not sure where I should start looking.

Why would my KVM guest spike CPU like this? Is there KVM logs where I can determine what exactly it is doing? Is there any way to limit the CPU usage and would that necessarily help?

Any help is appreciated. I love proxmox and use it for all my homelab needs to experiment but it's become unusable for me and I want to continue to use it.

My feeling is that it has to do with recent updates, either 3.2 or 3.3, as this was never a problem in 3.1. I know that's very vague and I'm willing to wipe and re-install in steps.

 

[Anderath]

So I've just tested bringing up 2 windows servers 2008r2 VMs to stress the server and it appears the KVM activity is idle for the Linux Mint VM, yet, once you move around the menus(In Linux Mint) after a while while the server is under stress, the menus start to mess up again.

To reiterate, display is still messed up regardless of how much KVM processes take up CPU. Rebooting the Linux Mint guest VM clears the issue.

My windows VMs are fine. Could it be possible some library is messed up that KVM uses for Linux machines as opposed to Windows?

 

[Iluciv]

So I've just tested bringing up 2 windows servers 2008r2 VMs to stress the server and it appears the KVM activity is idle for the Linux Mint VM, yet, once you move around the menus(In Linux Mint) after a while while the server is under stress, the menus start to mess up again.

To reiterate, display is still messed up regardless of how much KVM processes take up CPU. Rebooting the Linux Mint guest VM clears the issue.

My windows VMs are fine. Could it be possible some library is messed up that KVM uses for Linux machines as opposed to Windows?

I have the same issue with an lubuntu vm, if I reboot the vm then it's fine for a little while then the text doesn't draw properly on the screen and a remote session it pretty much useless. Nothing is taxing the VM resources too much and it doesn't matter if I allocate more resources to the vm the same thing happens.

Any tips on where I could look for causes would be great? Would it be graphical or bandwidth?

 

[nethfel]

I can't say I know an answer to your issue, but I am curious - on the host side, it looks like it's consuming a ton of CPU cycles, what does it look like inside the guest in terms of what's using all of the CPU cycles?

 

[manu]

I can't say I know an answer to your issue, but I am curious - on the host side, it looks like it's consuming a ton of CPU cycles, what does it look like inside the guest in terms of what's using all of the CPU cycles?

yep that's a point. To debug a bit this issue I would suggest you the following:

start a ssh shell session to your guest, and run htop in the ssh session, to monitor what's going on( since you're doing it outside the NoVNC / spice console ) it should remain responsive

generally spice should give you better performance if you run a gui on the guest, so I would concentrate on that