What is the impact of cache coherence on multithreading?

Can you explain what cache coherence is in the context of multithreading?

Cache coherence refers to the consistency of data stored in local caches of a shared resource. In multithreading, it ensures that all threads see the same data values, preventing issues like stale data.

Why is cache coherence important for performance in multithreaded applications?

It's crucial because it minimizes the overhead of data synchronization. Without proper cache coherence, threads may work with outdated data, leading to incorrect results and performance bottlenecks.

What are some common protocols used to maintain cache coherence?

Common protocols include MESI (Modified, Exclusive, Shared, Invalid), MOESI, and MSI. These protocols help manage how caches interact and maintain consistency.

How does cache coherence affect scalability in multithreaded systems?

Cache coherence can limit scalability because as more processors are added, the complexity of maintaining coherence increases, potentially leading to performance degradation.