Performance evaluation of network processor architectures:: combining simulation with analytical estimation

The designs of most systems-on-a-chip (SoC) architectures rely on simulation as a means for performance estimation. Such designs usually start with a parameterizable template architecture, and the design space exploration is restricted to identifying the suitable parameters for all the architectural components. However, in the case of heterogeneous SoC architectures such as network processors the design space exploration also involves a combinatorial aspect-which architectural components are to be chosen, how should they be interconnected, task mapping decisions-thereby increasing the design space. Moreover, in the case of network processor architectures there is also an associated uncertainty in terms of the application scenario and the traffic it will be required to process. As a result, simulation is no longer a feasible option for evaluating such architectures in any automated or semi-automated design space exploration process due to the high simulation times involved. To address this problem, in this paper we hypothesize that the design space exploration for network processors should be separated into multiple stages, each having a different level of abstraction. Further, it would be appropriate to use analytical evaluation frameworks during the initial stages and resort to simulation techniques only when a relatively small set of potential architectures is identified. None of the known performance evaluation methods for network processors have been positioned from this perspective. We show that there are already suitable analytical models for network processor performance evaluation which may be used to support our hypothesis. To this end, we choose a reference system-level model of a network processor architecture and compare its performance evaluation results derived using a known analytical model [Thiele et al., Design space exploration of network processor architectures, in: Proc. 1st Workshop on Network Processors, Cambridge, MA, February 2002; Thiele et al., A framework for evaluating design tradeoffs in packet processing architectures, in: Proc. 39th Design Automation Conference (DAC), New Orleans, USA, ACM Press, 2002] with the results derived by detailed simulation. Based on this comparison, we propose a scheme for the design space exploration of network processor architectures where both analytical performance evaluation techniques and simulation techniques have unique roles to play. (C) 2003 Elsevier Science B.V. All rights reserved.