Powermanagment and C-states on an x86_64 hardware

Hardware Questions and Recommendations
1

Hi,
I'm building an x86 firewall (an old Supermicro motherboard and a E3-1290 V2 Xeon). Previously I planned to use OPNsense but since the power management is very funky (meaning probably non existent) I scrapped that plan.
But I did find this very interesting github comment about how low C-states can completely scramble packet timing.
Is that true even under the Linux kernel? Is low c-states and good power managment impossible on x86 hardware?

2

That is true, I run OpenWrt on a Intel J4115 and latency to the gateway is 0.3 ms while I run stress-ng. Latency to the gateway in idle is 3ms. But that gets better the newer the hardware because the idle throughput gets higher and higher every gen.

3

So I guess I can kiss any CPU related power saving goodbye. Well that kinda sucks.