Windows VM slower performance with Passmark vs Ubuntu VM

[Kim Naru]

Summary : A Windows VM(KVM) on 22.04.3 is 10%(SMT off) to 16%(SMT on) slower running Passmark vs a Ubuntu 22.04.3 VM(KVM). The results should be within 1% of each other.

System Information :

Dell - AMD EPYC 7543 32-Core Processor, 2801 Mhz, 32 Core(s), 32 Logical Processor(s) Zen 3 (Milan)
BIOS - 2.12.4 FW (iDRAC Firmware Version 7.00.30.00)
NUMA Nodes Per Socket 1(default)
Memory - 512 GB of DRAM DDR4
OS : Ubuntu 22.04.3

Setup:

Install Ubuntu 22.04.3 and then setup 2 VMs one with Win 22 std. and another one with Ubuntu 22.04.3. Install Passmark benchmark on both the VMs and then run the “Single CPU Threaded” benchmark on both the OS with SMT enable and disable mode.

 Passmark Download link : https://www.passmark.com/products/pt_linux/download.php
Linux Setup version:
PerformanceTest Linux x86 64-bit
5.4 MB, v11.0 Build 1002, October 19 2023

Microsoft setup version:
Download PerformanceTest 11.0 x86
102 MB, Build 1007
For Intel and AMD x86 CPUs

Results :

***********
Bare metal
***********

Windows 2022
------------

SMT ON: Win22 VM 1% slower
SMT OFF: Win22 VM 1% slower

SMT Run1 Run2 Run3 Average
On 2766 2768 2771 2768.333333
OFF 2773 2766 2765 2768

Ubuntu 22.04
------------

SMT Run1 Run2 Run3 Average
On 2777 2777 2775 2776.333333
OFF 2798 2792 2792 2794

--------------------------------------------

****
KVM
****

SMT ON : Win22 VM 16% slower
SMT OFF: Win22 VM 10% slower

Host: Ubuntu 22.04 VM: Win server 22 VM - Single CPU Threaded

SMT Run1 Run2 Run3 AVERAGE
On 2356 2287 2289 2310.666667
OFF 2424 2459 2566 2483

Host Ubuntu 22.04 KVM with Ubuntu 22.04 VM - Single CPU Threaded
SMT Run1 Run2 Run3 AVERAGE
On 2730 2741 2729 2733.333333
OFF 2745 2746 2746 2745.666667

[Jeff Lane  (bladernr)]

Is this also an issue on Zen 4? What about Zen 2? I'm wondering if this is specific to Zen 3 or more generic to AMD and KVM setups?

[Kim Naru (kim-naru)]

The issue has been seen on Zen3 & Zen4. Don't know about Zen2

[Kim Naru (kim-naru)]

It appears the CPU boost support on KVM doesn't handle Windows VM, hence the lower numbers on a Windows VM vs a Ubuntu VM.

PassMark – Single Threading measurement, the majority of Perf Score are relied on vCPU Clock Speed.

Is this a know limitation?