Upgrading CPU decreased performance


Nov 27, 2021
I upgraded my cpu from 3900x to 4950x. And now I get screen tearing with my Ubuntu20 guest.

I have 128GB ram 60 GB dedicated to this VM.
Tried with another VM and have similar problem.
The performance-part is quite sef-explanatory: The new CPU has more core, but less frequency, so any single-thread performance benchmarks (and this is the most real-world-usage) is worse. Most VM system I've ever seen make exactly this mistake and ask then why the performance of application xyz is not good. Yes, you can virtualize a lot more machines (if you really need the CPU power), with a CPU that has more cores, but the overall performance is always decreased and most of the time, you're limited in RAM anyways.

Is this screen tearing with PCIe passthrough?
Thnaks for the answer @LnxBil UI is not just slightly slower. It is very bad. I almost dont use the UI now and use ssh, even VSCode over ssh.

I have 1 main VM. Most of the time I do not have much going on in parallel, but I love the option of starting second machine doing something there and closing it without the need to shutdown my main vm. Proxmox for me replaces dualbooting.

I have 128 GB ram 64 GM dedicated to the main VM no baloon
Storage is on NVME
RTX 3090 is dedicated to this VM and yes it is with PCIe passthrough
I had not heard about the 4950X before. Is it an official CPU or an ES? If it's a newer Zen generation, make sure to update your motherboard BIOS, clear CMOS and make sure to enable PBO and other settings again.


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