Mastering Cache-Conscious Data Layout in Rust: Field Zoning and the 128-Byte Rule

Cache-Conscious Data Layout in Rust: Field Zoning, False Sharing, 128-Byte Rule

I explore how to design high-performance multi-threaded structures in Rust by deliberately zoning fields based on which core accesses them. By separating producer and consumer hot paths and applying the 128-byte alignment rule, we eliminate false sharing that silently serializes cores. Using a single-producer single-consumer ring buffer as an example, I demonstrate why `#[repr(C)]` is essential for locking down memory layouts and how strategic padding prevents costly hardware coherence traffic.

"Two cores writing to different fields that happen to share a 64-byte cache line will quietly serialize each other through the hardware coherence protocol - a pathology called false sharing."