Managing changes to a packet-processing virtual machine's instruction set architecture over time

Abstract

We describe an approach to deploying only those bytecodes that can be executed by the current operating system and hardware resources in an environment that combines parallelism, processor heterogeneity and software-defined networking (SDN) capabilities. Packet processing's escalating speed requirements necessitate parallel processing and heterogeneous, specialised processors acting as accelerators. We use bytecodes for a virtual machine to drive the dissimilar processors with interpreters running in parallel. Since processors and SDN are evolving, bytecodes must evolve as well. We must execute reliable programs for packet processing, so we need to deploy only bytecodes that the interpreters and system resources can support. Our solution combines: 1) correlating supported features, interpreter versions and hardware variants in a manifest file; 2) instrumenting a compiler to recognise key feature use; 3) carrying detected feature data in an object module section; 4) running a checking tool at various stages to prevent compiling or deploying a bytecode that cannot be correctly executed. The scheme has handled deprecating features and adding a broad variety of new features. It has been stress-tested by significant changes in hardware variants.