Apache Derby SMP scalability: Investigating limitations and opportunities for improvement

Abstract

This report investigates the B-Tree access method of Apache Derby. Apache Derby is an open source Java database system. The detailed focus of the report is on performance aspects of the Derby page latch implementation. Our focal point is the interaction between the B-Tree access method and page latching, and the impact of these components on the ability of Derby to scale on multiprocessor systems. Derby uses simple and in the single-threaded case inexpensive exclusive-only page latches. We investigate the impact on scalability of this design, and contrast it with a version of Derby modified to support both shared read-only and exclusive page access for lookups in index structures. This evaluation is made for single-threaded as well as multi-threaded scenarios on multiprocessing systems. Based on analyses of benchmark results and profiler traces, we then suggest how Derby may be able to utilize modern Java locking primitives to improve multiprocessor scalability.