Virtual Machine Services:An Opportunity for Hardware Customization

This paper considers the intersection of two computing trends: (1) Computer architecture design is now constrained by power, instead of transistor count, which is leading to architecture heterogeneity and customization. (2) Software developers increasingly choose managed languages, such as JavaScript, PHP, Java, and C#. Managed languages require a VM (Virtual Machine), which executes services such as profiling, compilation, scheduling, and memory management together with every application. The ubiquity of VM services makes them a perfect test case for potential improvements in energy through the use of hardware heterogeneity. This paper uses systematic exploration of hardware features such as frequency and voltage scaling, cache size, hardware parallelism, and gross microarchitecture design on the power, and performance of VM services. It thus evaluates this potential on actual hardware, rather than through simulation. We study Just-in-Time (JIT) compilation, interpretation, and memory management. We find that VM services consume around 20% of energy on average. Compared to application code, the memory manager and interpreter offer substantially different workloads and do not uniformly benefit from high performance architectural features. A heterogeneous multicore processor thus has the potential to substantially improve energy of managed applications with cores customized for VM services.