What is cache coherence in multiprocessor systems?

Can you explain what cache coherence means in multiprocessor systems?

Cache coherence refers to the consistency of data stored in local caches of a multiprocessor system. It ensures that any changes made to a shared data item in one cache are reflected in all other caches.

Why is cache coherence important for performance?

It's crucial because it prevents data inconsistency and ensures that all processors have the most up-to-date data, which enhances performance and avoids errors.

What are some common protocols used to maintain cache coherence?

Common protocols include MESI (Modified, Exclusive, Shared, Invalid), MOESI, and MSI, each with different strategies for managing cache states.

Can you give an example of a cache coherence problem?

Sure! A classic example is the 'false sharing' problem, where two processors modify different variables that reside on the same cache line, leading to unnecessary cache invalidations.