Netbird uses kernel Wireguard module, right. Is there a way to measure kernel memory / CPU usage attributed to Wireguard?
Zerotier, which has the lowest memory usage, does not use Wireguard at all, they have their own custom protocol and it's userspace AFAIK.
Tailscale is written in Go with lots of dependencies. It also has a lot more features, to the point some would call that too much 😅 Zerotier is pretty lean and in C. That would explain those 55 MB idle memory usage difference. But those 245 MB after iperf3 test though... I can't explain, but it's consistent and repeatable.
After 10 minutes PSS was back to ~74 MB