The comfort automatic tuning project

摘要

This paper reports on results and experiences from the COMFORT automatic tuning project. The objective of the project has been to investigate architectural principles of self-tuning database and transaction processing systems, and to develop self-tuning methods for specific performance tuning problems. A particular concern of the project has been to cope with workload dynamics and workload heterogeneity in multi-user systems. As a general guideline, an adaptive feedback control approach has been adopted, where observations of the current load characteristics are used to predict performance trends and to drive the dynamic adjustment of tuning parameters. As examples of these general principles, the paper discusses adaptive approaches to two specific tuning problems and the deeloped solutions. First, we present a self-tuning load control method that copes with overload caused by excessive lock conflicts that may occur during load surges. This conflict-driven load control method adapts the multiprogramming level of the system to the evolving load characteristics dynamically and automatically. Secondly, we discuss the self-tuning LRU-K database buffering method, which makes intelligent buffering decisions by dynamically tracking the access frequency of pages, thus coping well with evolving access patterns. We discuss the rationale of these two self-tuning methods in great detail and we present comprehensive performance evaluation experiments for both synthetic and trace-driven workloads.