High CPU usage after enable IOMMU

[Alex000ch]

Ive encountered an weired behaivior with one of my VE Hosts. I need to activate the IOMMU and i followed the described steps on the PM Wiki. Right after adding "intel_iommu=on" to /etc/kernel/cmdline and updating the kernel my PM Host is constantly on 40%- 90% CPU without anything running but PCI passthrough is doing its job.
As soon as i remove the IOMMU config my host turns back to normal.

Ive now running PVE 5.15.116-1 but had this issue also with 5.15.107-2.

Does anyone have me any advice to find the cause of my problem?

 

[Alex000ch]

Bump?

 

[leesteken]

Bump?

And there is nothing in the system logs? And you cannot find which process is using the CPU?

 

[Alex000ch]

And there is nothing in the system logs? And you cannot find which process is using the CPU?

Well, there is the main problem. There is no specific Service that consumes all the resources its more that every services need suddenly more power. For example even "top" peaks at 80%.
Im really not a Linux crack but the logs in /var/log seems fine.



But i just resolved the problem "by accident"...

The Server had an 4x MGig Network card installed which ive never used. So i just removed it and now everything works like a charm. Can someone maybe explain that to me?

 

[LnxBil]

Next thing I would have suggested is to look at the number interrupts thrown and compare that to running without iommu.