One of the most important design goals of current Peer-to- Peer (p2p) technology is to be able to offer its service to an arbitrary large number of users. Discrete event simulation is often applied to quantitatively and qualitatively evaluate the performance and scalability of such systems before they are deployed. However, the number of users, processes and events which can be simulated is limited by both the central memory and the time available. In this paper we present compact data structures and event design algorithms, which are intended to be a further step towards efficient simulation of large scale p2p systems. In particular, we give guidelines on how to increase the number of peers which can be simulated and show how to find a good trade-off between computational time and memory consumption in large scale p2p simulation.