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UDP RSS not working on Windows 10 with Intel NIC X550-T2


Dear Intel-Community,

we tried to acquire 10GBit/s of UDP traffic most of the time lossless (the measurement device is not capable to hold so much data in the own cache, so TCP is not a solution here) .

To test if we can acquire 10GBit/s of UDP traffic we bought 2 Intel X550-T2 NIC's and connected them directly over an 2 Meter Cat7 Cable. But we couldn't bring the receiver side to use more than one CPU to acquire the data over UDP, but using TCP strangely uses all 8 configured RSS queues also we get 10 GBit/s of traffic.
Also using Ubuntu Linux 20.04 works very well (10GBit/s UDP traffic 0% loss).

My question is now, how can we use the RSS also for UDP on Windows 10?
And if it does not work, why?

Receiver hardware:
Processor: AMD Ryzen 3900X
Motherboard: X570a-pro
RAM: 64 GB

Windows 10 Professional
Hyperthreading / SMT: Disabled (I don't know if this is required, but Microsoft states, that RCC only uses non SMT processors)
DMA-Coalescing: OFF
Receivebuffer: 4096
Flow control: Rx+Tx
Speed and Duplex: Auto
Interrupt  reduction: Enabled
Interrupt  reduction rate: Adaptive
IPsec Offload: OFF
IPv4 - checksum offload: Rx + Tx
Large-Send-Offload V2 (IPv4+v6): Enabled
Max. Rss Queues: 8 (I tested also 16, but that changed nothing)
Package priority and VLAN: Deactivated both (activating both changed nothing)
RSS: Enabled
TCP - Checksum offload (IPv4+v6): Rx + Tx
UDP - Checksum offload (IPv4+v6): Rx + Tx
Sending buffer: 16384
Connection event log: Enabled

Method of testing:
Since RSS is based on hashing of S/R IP + S/R Port, I started 10 receiving iperf3 servers on the receiver, each listening on different ports and started 10 sending clients on the sender.
Sending UDP packages occupies one whole CPU/core of the receiver, bot non of the other cores. And only 5GBit/s could be acquired.
Sending TCP packages occupies all the specified 8 receiving queues and 10Gbit's could be acquired.

Thank you for your help :).
Kind regards,
Fabian Keßler

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3 Replies

Hi Fabian_kessler,

Thank you for posting in our Intel® Ethernet Communities Page.

To better assist you, we need to get some logs from your system. It will tell us the different driver version and components installed on your system. Please download and run our Intel® System Support Utility from this page, After running it, you will be given an option to save the logs to a text file, please do so and attach the file on your reply.

We also want to ask if you are running the test in a virtual environment or on the local OS.

We look forward to hearing from you. If we do not get your reply, we will follow up after 3 business days.

Best Regards,

Alfred S

Intel® Customer Support

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Hi Fabian_kessler,

We are just following up.

It looks like you need more time to provide the information that we asked.

We will follow up again after 3 to 4 business days. Should we not hear from you, our system may automatically close the thread.

Best Regards,

Alfred S

Intel® Customer Support

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Hi Alfred,
I am very sorry, somehow I have overseen the push-up mails you send me.
I created those files on both computers, the receiver and the sender.
Is there a way to send you the files. I would be reluctant to distribute the data over a public channel.

Kind Regards,

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