CSIT/csit tg servers

DRAFT FD.io CSIT recommended server specification for Traffic Generator (TRex) used in FD.io performance tests.

TODAY - Deployed Traffic Generator (TG) Servers

All TG/TRex instances are based on Xeon servers
- SuperMicro 2 socket servers.
- Motherboards with max PCIe I/O for NIC cards.
For Xeon SUTs, same Xeon generation for TG
- 2n-clx, 2n-clx => CLX TG.
- 3n-skx => skx TG, SKX TG.
- 3n-hsw => hsw TG, HSW TG.
For Arm SUT ThunderX2
- 2n-tx2 => shared skx TG, shared SKX TG.
- shared TG has two TRex instances running in parallel, one per Numa.
For AMD SUTs, same AMD generation for TG
- 2n-zn2 => zn2 TG, ZN2 TG
for DNV
- 2n-dnv => shared skx TG, shared SKX TG.
- 3n-dnv => shared skx TG, shared SKX TG.

Standardise on a reference TG server
- Reduce amount of work involved in TRex calibration for tests with STL and ASTF APIs.
- Improve TG/TRex determinism of behaviour and performance.
- Get max performance from TRex.
Proposal
- Use Xeon ICX as the main TG server platform
  - Processor: ICX high end SKU (assume 8380), similar to what is used for SKX (8180) and CLX (8280).
  - Server/Motherboard: OEM motherboards with max PCIEe Gen4 I/O (as per current practice).
- Optionally consider lower power Xeon builds for lower end SUTs
  - e.g. for new Intel Atom / Snowridge SUTs?
  - e.g. for new Arm / Ampere SUTs?
    - The risk here is that underpowered TG may not be able to stress Ampere 80-core processor, in case we ever go that high on Arm SUTs.

Is CSIT project good to continue to have TG/TRex servers shared, e.g. TRex instance per Numa/socket? If yes, need to work out what "slower" SUTs / low-speed NIC we expect in the project going forward.
What is the status of TRex support for Arm, and expected performance?
- CSIT project doesn't have any experience running TRex on Arm.
- TRex documentation claims generic support for Arm, but no builds provided, need to compile from source.
- No / limited documented use of TRex on Arm servers.
If for the new builds in 2021 CSIT recommend ICX Xeon, but once SPR Xeon arrives in the future it will be faster.
- Meaning we always end up with a mix of TG server platforms, as is the case today.