Memory Ordering

Memory ordering is a concept in concurrent programming that defines the rules for how memory operations (reads and writes) are visible and ordered across multiple threads or processors in a shared memory system. It specifies the guarantees about the sequence in which memory accesses appear to occur, which is crucial for ensuring correctness in multi-threaded applications. This concept is fundamental to understanding and implementing synchronization mechanisms like locks, atomic operations, and memory barriers.

Also known as: Memory Consistency, Memory Model, Memory Barrier, Fence, Atomic Ordering

Why learn Memory Ordering?

Developers should learn memory ordering when working with low-level concurrent programming, such as in systems programming, embedded systems, or high-performance computing, to avoid subtle bugs like data races and ensure thread safety. It is essential for using atomic operations and lock-free data structures correctly, as improper memory ordering can lead to unpredictable behavior and hard-to-debug issues. Understanding memory ordering helps in optimizing performance by choosing appropriate synchronization primitives and avoiding unnecessary barriers.

Learning Resources

• docs: C++ Memory Model and Atomic Operations
• tutorial: Memory Ordering in Practice
• docs: Concurrency in Go: Memory Model
• docs: Java Memory Model Tutorial
• docs: Memory Ordering in Rust