Why std::memory_order_seq_cst is often overkill for single-producer single-consumer queues:

When writing a lock-free queue:

• Producer: Writes payload to buffer, then performs tail.store(newTail, std::memory_order_release).
• Consumer: Loads tail.load(std::memory_order_acquire), then reads payload.

release guarantees that all prior memory writes (the buffer data) are visible to any thread that executes an acquire load on that same atomic variable. On x86/x64, hardware already enforces TSO (Total Store Order), so acquire/release loads/stores compile to plain mov instructions with zero mfence penalty!

Great explanation. On ARM64 (which is weakly ordered), acquire generates LDAR and release generates STLR instructions, avoiding full DMB ISH memory barriers.

Lock-free algorithms without acquire-release semantics are a ticking time bomb on modern mobile and server processors.