vMX 18.2 on pure Linux (no VMs/nested virtualization); GNS3; "lite" mode; laptop with two-core 2.4GHz CPU (HT disabled) and 16GB of RAM; "halt_poll_ns=0".
Overall CPU utilization is 35..40% at idle.
I totally agree with @kechik, you (and me) can't do anything, Juniper software is just really CPU-intensive. An overhead of nested virtualization (using of EVE-NG or GNS3 VM) is way too small to be noticeable. And IBM wrote about "halt_poll_ns=0": "In a environment where CPU resources are highly over-committed, this setting might be counterproductive."
In my labs I extensively use logical systems and routing instances, so one vMX node is enough to emulate 10..20 routers. I understand that logical systems are not always suitable, that's just my case. vMX 14.1 is quite lightweight, but it lacks all this EVPN bells and whistles, and some configuration commands are a bit different, so it's not really useful now. That's my two cents. And, by the way, thank you for sharing vMX 21.2:)
