Reshape your layouts, not your programs: A safe language extension for better cache locality

Abstract

The vast divide between the speed of CPU and RAM means that effective use of CPU caches is often a prerequisite for high performance on modern architectures. Hence, developers need to consider how to place data in memory so as to exploit spatial locality and achieve high memory bandwidth. Such manual memory optimisations are common in unmanaged languages (e.g. C, C++), but they sacrifice readability, maintainability, memory safety, and object abstraction. In managed languages, such as Java and C#, where the runtime abstracts away the memory from the developer, such optimisations are almost impossible.We present a language extension called SHAPES, which aims to offer developers more fine-grained control over the placement of data, without sacrificing memory safety or object abstraction. In SHAPES, programmers group related objects into pools, and specify how objects are laid out in these pools. Classes and types are annotated by pool parameters, which allow placement aspects to