Applicability of general purpose processors to network applications

In this paper we look at the applicability of some of the features commonly found in general-purpose processors to network applications. Specifically we evaluate the benefit of in-order vs. out-of-order instruction issue, multiple issue, and subword parallelism. We find that issuing instructions out-of-order improves instructions-per-cycle (IPC) performance by 96% over issuing instructions in-order. We also find that CPU performance does not scale linearly with issue width. A 2-way issue out-of-order processor is probably a better choice than a 4-way or 8-way issue processor. We find there is a good amount of subword level parallelism in network applications. We evaluate the benefits of a hardware solution to exploit this parallelism. This does not require any support from the compiler/programmer, and leads to an improvement of 13% in IPC. It also saves energy in integer register file by 39%. Combining all three mechanisms leads to an improvement of 89% in IPC compared to a 4-way issue in-order processor.