RSS CPU usage not consistent between Windows Server 2012R2 reboots

[KBARO]

I have a dual port 10 GB NIC card using the 82599 controller. I am using the latest PROWin64 driver, Version 23.5.2. I have an application that send 4.5 Gbps on a single port. the data is split beween two UDP port numbers. I have RSS enabled and set to 2 CPUs. On some reboots, the driver utilizes two CPUs to process the data flow but on some reboots, the driver uses only once CPU. Why can I not consistently get the RSS to split the processing for my two UDP port application?

[Mike_Intel]

Hello KBARO,

I am just checking if you are having issues with the other NIC installed in your system which is X540.

If you have questions, please let us know. 

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel

[KBARO]

Hi Mike,

The device I communicate with transfers data at a burst rate of 4.5 Gbps over fiber, so i cannot run the same test with the RJ45 motherboard x540 device.

Do you have any description on how the driver hashes the various UDP packets to assign them to different CPUs?

Thanks

Ken

[Mike_Intel]

Hello KBARO,

Thank you for the clarifications. Let me check on this and update you again.

If you have questions, please let us know. 

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel

[Mike_Intel · Accepted solution]

Hello KBARO,

Thank you for patiently waiting. I have an update on this issue.

Please verify if you already tried the following combination:

1. Set the RSS load balancing profile to "Closest Processor". Setting Closest Processor Static will assign the processors at boot and won't change them as load increases.
2. Set the MaxRSS queue to "2"

For questions related to RSS, please find answer below:

Q - How does your driver decide to use one or two CPUs when receiving the data stream?

A - Intel driver works in accordance to how Microsoft defines the RSS capability. It uses hash function to computer for LSB then assign to the defined cores. Please refer to links below for additional information. Share the 3rd party link disclaimer.

RSS configuration - https://docs.microsoft.com/en-us/windows-hardware/drivers/network/rss-configuration

RSS hashing types - https://docs.microsoft.com/en-us/windows-hardware/drivers/network/rss-hashing-types

If you have questions, please let us know. 

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel

[KBARO]

Thank you Mike. I think I tried the Closest processor static option, but I won't be able to test this further for a couple of weeks. I was hoping that I could easily control the hashing function to get the behavior I want. I will look into that as well. Thanks again.

[Mike_Intel]

Hello KBARO,

Base the SSU that you provided, your RSS load balancing profile was set to "Closest Processor Static". However our suggestion is to try out "Closest Processor".

Please try that and check if there will be changes. Can you also tell us can you provide an update?

If you have questions, please let us know. 

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel

[Mike_Intel]

Hello KBARO,

Just want to check if you tried our last recommendation.

If you have questions, please let us know. 

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel

[Mike_Intel]

Hello KBARO,

I just want to check if you still have questions or clarifications specially with our last recommendations.

If you do, please let us know.  

Best regards,

Michael L.

Intel Customer Support

A Contingent Worker at Intel