Faster slab reassignment in memcached
Daniel Byrne, Nilufer Onder, Zhenlin Wang · Proceedings of the International Symposium on Memory Systems · 2019
Web applications, databases, and many datacenter services rely on in-memory key-value stores to cache frequently accessed data. In this work, we focus on a commonly used system, memcached, where even small performance improvements can result in large end-to-end speed ups in request latency. memcached organizes its memory into slabs that belong to different classes corresponding to object sizes. Many prior works have explored the problem of how many slabs should each class be assigned in the face of dynamic workloads, typically reassigning hundreds of slabs during a reassignment. However, we find that as workloads scale and applications use increasing amounts of memory, the current reassignment mechanism in memcached is inefficient. In fact, we measure that reassignments can take millions of requests to complete.