[VFIO][Ryzen 5] Report actual CPU frequency to guest

Operating Systems & Open Source Virtualization
1

Hi there!

I am running on PopOS 19.10 as host, and Windows 10 Pro on my guest machine. Very happy with my settings and the guest performance so far!

There is some “cosmetics” which is bothering me.

My Ryzen 5 2600x is overclocked up to 4.2 GHz when boosting. PopOS is showing the actual correct clock speeds.

But my guest is locked to 3.6 GHz; at least displaying so in the taskmanager.

Is there a way to for my guest system to show the real clock speed?

Godspeed

2

I kinda want to put my adventures of virtualization on 3rd gen Threadripper in one giant thread.

But just to help you out.
Well no, unless you overclock the multiplier aka not boosting but a fixed frequency.

However, if you don’t use isolcpus and the derivatives of it. The CPU on the host will boost.
Why do I say that? Isolcpus and its derivatives locks the CPU to its base frequency.

How did I verified that? Using this command:

watch -n.1 “cat /proc/cpuinfo | grep “^[c]pu MHz””

Not a perfect command by any means. You for example cannot see which CPU core each frequency is. I could use some help on that department.
Any case you can see your frequency in real time.
This is how I verified that my 3960x Threadripper was boosting correctly(Al though max frequency being 4.2GHZ is far below advertised 4.5 GHZ).

Just additional note: If you have Cool and Quiet feature on the bios, then you can set the governor in Linux. If not then it doesn’t allow you that. What happens under the hood, is something that I cannot answer you definitely. It is something you have to try yourself and see if there is improvement in performance.

I for one did just that in cinebench using R7 2700x:

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