Minimizing Cache Misses in an Event-driven Network Server: A Case Study of TUX

We analyze the performance of CPU-bound network servers and demonstrate experimentally that the degra- dation in the performance of these servers under high- concurrency workloads is largely due to inefficient use of the hardware caches. We then describe an approach to speeding up event-driven network servers by optimizing their use of the L2 CPU cache in the context of the TUX web server, known for its robustness to heavy load. Our approach is based on a novel cache-aware memory alloca- tor and a specific scheduling strategy that together ensure that the total working data set of the server stays in the L2 cache. Experiments show that under high concurrency, our optimizations improve the throughput of TUX by up to 40% and the number of requests serviced at the time of failure by 21%.