[Intel-wired-lan] Slow e1000e Network Interface with different kernel

[Marco Witte <m.witte@neusta.de>]

Scenario: Plugin into network, establishes link and IP is assigned.
scp from another machine in the same subnet gives approx. 1kb/sec.
Cross check with an usb 3 dock with integrated network adapter. Full speed.

Kai Heng-Feng build a patch for tgp https://lkml.org/lkml/2021/7/12/2927
His deb kernel packages with that patch based on 5.10.x kernel ran full 
throttle on this machine.
However this was the only successfull attempt to get full speed.

The Kernel Mainline 5.13. contains visual similar patches, but they 
still have the slow down on the same machine.
Some people suspect pcie changes at that point.

Some curious fact I found out while testing: I booted up a manjaro 
(current) usb stick and had full speed on the e1000e. Then I installed 
manjaro from that stick to the harddrive. Booted that and it didn't 
perform well.

As this is my first rodeo on this mailinglist, I need to reference some 
information:

Referencing: https://bugzilla.kernel.org/show_bug.cgi?id=213377
Here is the launchpad: 
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1927925
e1000e Sourceforge bugreport(s): https://sourceforge.net/p/e1000/bugs/681/
This is still an issue with all current mainline kernels. Last test was 
5.14 RC7

I can provide any output you need.