Latency-Optimized Checkpoint Recovery Algorithms for Massively Multiplayer Online Games

Massively Multiplayer Online Games (MMOs) are long-lived, interactive virtual worlds in which tens of thousands of people play together. In order to provide highly immersive experiences, MMO servers must support extremely high update rates – often hundreds of thousands of updates per second. A major concern for MMOs is to provide durability for the virtual world while limiting the overhead and perceived latency spikes introduced in the game. Recent work has shown that existing checkpoint-recovery algorithms developed for main memory DBMSs can be applied to MMO workloads but there is no single algorithm which outperforms all others over a wide range of update rates.. In this paper we propose two novel checkpointing algorithms that trade additional space in main memory for significantly lower latency. Compared to previous work, our new algorithms do not require any locking nor do they require bulk copies of the game state. Our experimental evaluation shows that our new algorithms attain nearly constant latency and achieve more than an order-of-magnitude lower overhead than the best previous methods.