[Server] Do you set affinity to one core or all cores?

What is the better otpion if you are running multiple rust servers on the same machine (let's say two).
Do you set affinity of each process to one cpu core or let all servers use all cores (set affinity to all)?

Any input about the topic is welcome and tell me why you think so.

 

Generally 4 cores each, without affinity set I've noticed that a single server will lag like shit.