What are some examples of cache coherence issues?

What are some examples of cache coherence issues?

Cache coherence issues occur when multiple processors have their own caches and they don't synchronize properly. For example, if one processor updates a value in its cache, other processors may still have the old value, leading to inconsistencies.

Can you give me a specific scenario where this happens?

Sure! Imagine a multi-core processor where Core 1 updates a variable in its cache. If Core 2 reads that variable before it gets updated in its cache, it might operate on stale data, causing incorrect results.

How do systems typically resolve these issues?

Systems use protocols like MESI (Modified, Exclusive, Shared, Invalid) to maintain cache coherence. These protocols ensure that when one cache updates a value, other caches are notified to update or invalidate their copies.

What are the performance implications of cache coherence?

Cache coherence can introduce latency due to the overhead of maintaining consistency, which can slow down system performance, especially in multi-core systems with high communication demands.