Efficient code management for dynamic multi-tiered compilation systems

Abstract

Managed runtime environments (MREs) like web browsers or the Java Virtual Machine (JVM) include multiple dynamic compilers (or compiler configurations) to provide a good tradeoff between compilation speed and generated code quality: Longer compilation times typically imply better code quality and hence better peak performance than shorter compilation times, which provide good warmup/startup performance and lower peak performance. A system that uses multiple compilers is referred to as a multi-tiered compilation system.Multi-tiered compilation systems pose a significant challenge to the code cache, since methods can be compiled multiple times at different compilation levels. The characteristics of muti-tiered compiled code (e.g., lifetime, size, etc.) can lead to an inefficient code cache usage. This paper discusses the challenges in the context of the Java Virtual Machine (JVM) and proposes a new code cache design that aims at solving these challenges.A detailed performance evaluation shows that our new code cache design improves overall performance by up to 7%. The performance gain results from a combination of faster code cache sweeping as well as better instruction TLB and instruction cache behavior.