Large applications reliant on dynamic compilation for performance often run in horizontally scaled architectures. When this is combined with frequent deployment or demand-based scaling, hardware capacity is lost to frequent warmup phases due to the need to recompile the code after each start of the virtual machine (VM). Moreover, the individual VMs waste hardware resources by repeating the same compilations.

Offloading compilation jobs to a dedicated compilation server can mitigate these problems. Such a server can compile the code in a mode where the compilation result is reusable for multiple VMs. The goal is to save compilation resources, such as CPU and memory, and potentially improve the warmup time of individual VMs.

This paper investigates the options to reuse previous compilation results within a high-performance VM. We present an empirical study using the GraalVM compiler and the HotSpot Java VM. To facilitate code reuse, we introduce an approach that compiles code into a reusable high-level intermediate representation (IR). This approach defers VM-specific optimizations until the time of reuse. The incurred slowdown of such code varies by workload, ranging between a negligible impact and a 6x slowdown. Although deferred optimization impacts the efficiency of particular code patterns, such reused code still performs significantly better than that compiled by a lower-tier compiler. Therefore, the presented approach can form the foundation for improving warmup times in certain workloads.