it sounds you want to lower the latency of network transfers? which type of traffic do you have (using the machine as a router that has to forward packets with minimum latency or an application on the machine)? which protocol do you use, e.g. does it retransmit like tcp in case of packet drop or errors or do you use udp and can ignore missing data? is the latency really in the networking stack or in the network and protocols? which type of interconnect do you have, i.e. which bandwidth and maximum packet size? are there any routers/switches/hubs involved? does the medium have any latency guarantees? do you use quality of service tags and traffic shaping or a more advanced type of priorization?

how to measure decrease of performance? Anonymous obviously just run the same application on each of the kernels and measured the time and/or monitored the interface data rates. and measured the latencies, which in the easiest case is something like ping, but may involve interface timestamps or similar.