On Tue, Jun 10, 2025 at 10:25 AM dhayanands--- via Users <users@ovirt.org> wrote:

Hi team,

We’re facing a strange issue with network performance on one of our oVirt hosts and would like to get insights or guidance on possible misconfigurations or compatibility problems.

Environment Details:
oVirt Version: 4.5.5

Cluster CPU Type: Intel IceLake Server Family (default)

Host A (Issue observed):

CPU: Intel Xeon Platinum 8562Y+ (Sapphire Rapids)

CPU Family/Model: Family 6 / Model 207 / Stepping 2

Host B (Working fine):

CPU: Intel Xeon Gold 6354 (Ice Lake)

CPU Family/Model: Family 6 / Model 106 / Stepping 6

Problem Description:
We have a VM (kitsu) that was initially hosted on botovirtnode-006 (Platinum 8562Y+). The VM showed very poor download speeds (~10 Mbps), while upload was fine (~680 Mbps). After migrating the same VM to another host (botovirtnode-001 with Gold 6354 CPU), network performance drastically improved:

Test    On Affected Node        On Healthy Node
Download        ~10 Mbps        ~920 Mbps
Upload  ~680 Mbps       ~760 Mbps

This clearly indicates a host-specific issue, most likely related to hardware compatibility or CPU feature masking.

Troubleshooting Done:
Verified VM configurations (same on both hosts).

Tested with speedtest-cli multiple times to confirm.

Confirmed that VM virtual NIC, vNIC profile, and vSwitch settings are identical.

Both hosts are part of the same cluster using the default Intel IceLake Server CPU type.

Suspect the issue is due to CPU feature mismatch or unsupported stepping/model in the cluster’s CPU type.

Hi,

as a previous Intel employee, just to point out that 8562Y+ is an Emerald Rapids CPU, the 5th Generation of Intel Xeon Scalable platform (Sapphire Rapids is the 4th, pin/to/pin compatible with Emerald Rapids).

That said, I would go analyzing the network cards on your newer server, to verify the kernel driver used by the OS and eventually some default applied settings that could be suboptimal for your config.

Also, if you are using bonding, if the configuration is the same, supposing the upstream switching type is the same

Link speed, duplex got and so on.

I don't think the root cause is the cpu, as you have 32 vs 18 cores, base freq 2.8 vs 3 GHz, but boost freq 4.1 vs 3.6 GHz, DDR5 vs DDR4, PCIe 5 vs 4

Which performance profile are you using in BIOS for the 8562Y+, are you using speed-step technology and lowering the number of active cores? See here: https://www.intel.com/content/www/us/en/products/sku/237558/intel-xeon-platinum-8562y-processor-60m-cache-2-80-ghz/specifications.html

Feel free to share more info on the network cards settings.

Eg using "lspci -vk" where you also get the kernel driver in use. And "ethtool net_interface" and "ethtool -k net_interface" to see aquired settings

HIH,

Gianluca