Intel i9 13900k bad multicore perfomance

[katoffer]

Hello there everybody,

i am running an Windows 11 VM on my proxmox server (newest BIOS and all settings double checked on the BIOS side).
I use a i9 13900k and 64 GB 3200 mhz DDR4 RAM.

Somehow no matter what i am doing i get disappoting multicore benchmark results in the Windows 11 VM. I tried 3DMark an Geekbench and on both the multicore perfomance stays nearly 50% behind the bare metal benachmark. Single core is about 10% only under, which is totaly fine.

Attached some screenshot of my VM and CPU settings and benchmark results. (CPU Type host, NUMA on, PVE 8.1, q35-8.1 ....)

Has anybody of you beatiful people an idea what this could be ? Did i miss any settings or some magic switch ? Its the only machine that is having these troubles here i am getting crazy...

-

 

[katoffer]

Bare Metal results on Geekbench for the processor

 

[Dunuin]

Don't allocate that VM all 32 threads. PVE needs some threads too. If PVE has to wait and can't hypervise because the CPU is at 100% utilization this wil also slow down all the guests.

You might get some better performance but lowering security by disabling mitigations on the PVE host.

 

[katoffer]

Thank you Dunuin . It helped a little and i got around 1000 points more in the benchmark (stable around 14000 points in geekbench muliple testings). Nonetheless its still around 40% slower in multicore bench. Is it supposed ? Lack of right support from proxmox ? Or any strang setting i choose ?

 

[Dunuin]

Did you disable mitigations by adding params to the bootloader?: https://forum.proxmox.com/threads/disable-spectre-meltdown-mitigations.112553/post-485863

Config looks fine. Disabling KSM and ballooning might also give some more performance.

And have a look at the CPU governor and power settings. That those are set to maximum performance.

 

[katoffer]

Hey Dunuin - like yesterday thank you very much for your support (and fast response!). I checked the cpu governor (was already on perfomance mode) and deactivated KSM. Also deactivated the mitigations per bootloader but sadly none of this got me more perfomance on the benchmark. Still hovering at 14000 points in geekbench and 15000 in 3DMark. Its really wrecking my nerves. Maybe there is some specila setting in BIOS, i will check there again (slowly getting into the real manufactors professional depths of all the settings etc. there...)

 

[cfgmgr]

What version of virtio drivers are being used?

 

[katoffer]

What version of virtio drivers are being used?

0.1.240-1

 

[cfgmgr]

0.1.240-1

I don't have immediate experience with Windows on KVM/Proxmox but perhaps trying an older driver might be worth while? Seen some success around the forums with that.

 

[_gabriel]

edited: wrong info , missing my test was done with a VM with 8 Limited CPU within windows with msconfig.

Last time checked on laptop i5-12450H, pve 8 allocate only P cores to VM.
have you checked number of cores within Guest ?
imo, you're limited to 16 vcpus by default, even if you set 32.
8x E cores will be used by pve.

 

[cfgmgr]

Last time checked on laptop i5-12450H, pve 8 allocate only P cores to VM.
have you checked number of cores within Guest ?
imo, you're limited to 16 vcpus by default, even if you set 32.
8x E cores will be used by pve.

Oh this is interesting! Is this documented anywhere? Would love to read on it!

 

[_gabriel]

oups , wrong info, need correction : I was testing the windows host OS as a VM with msconfig within Guest set to 8 CPU max.
Just retried and all cores are assigned.
Will compare bare metal vs VM with PerformanceMark v11 from cpubenchmark.net

 

[katoffer]

I don't have immediate experience with Windows on KVM/Proxmox but perhaps trying an older driver might be worth while? Seen some success around the forums with that.

Hey there cfgmgr! Thank you for your idea. I tried some older virtio versions (0.1.210-2 and older) and got to 15000 points now in geekbench. Step by step folks and thanks to you too _gabriel !