Rethinking the Memory Hierarchy for Modern Languages

Abstract

We present Hotpads, a new memory hierarchy designed from the ground up for modern, memory-safe languages like Java, Go, and Rust. Memory-safe languages hide the memory layout from the programmer. This prevents memory corruption bugs and enables automatic memory management. Hotpads extends the same insight to the memory hierarchy: it hides the memory layout from software and takes control over it, dispensing with the conventional flat address space abstraction. This avoids the need for associative caches. Instead, Hotpads moves objects across a hierarchy of directly addressed memories. It rewrites pointers to avoid most associative lookups, provides hardware support for memory allocation, and unifies hierarchical garbage collection and data placement. As a result, Hotpads improves memory performance and efficiency substantially, and unlocks many new optimizations.