In order to achieve maximum throughput, is it good to have the number associations equal to total number of cores used.
So, if I am using performance mode on 3100B that means all together I have 2 (ports) x 6 (Cores, each port) = 12 cores with 2 ports in performance mode, so the number of associations should also be 12.
If you have 6 cores per port on the server, then it is best to have a multiple of 6 server IPs. If you use a range of IPs in the server subnet, then the IPs will be split among however many cores there are. If your action list only hits ONE IP, then only ONE server will be active. If instead you use 6 IP addresses in your action list, and create 6 server associations with one IP each, then as the test runs, each line of the action will hit a separate server core. This manual load balancing is the best way to tune your test for max performance.
The same engineering applies in functional mode too.
The another best way is to use canned test, mentioned in FAQ12308